Throughout the Word of God, water is a symbol, a “type,” of the spirit of God, and is often used analogously to represent holy spirit, that is, the divine nature and power of God. In Scripture, God is also known as “the Holy Spirit.”  In Jeremiah 2:13, for example, God refers to Himself as a “spring of living water” (see also Isa. 44:3 and 4). Think about water and what it means to you. Water is essential to life—we die without it. The average person can go about 60 days without food before he starves to death, but one can go only about three days without water, because it is so vital. In fact, the human body is mostly water. Whenever someone forsakes God, the spring of living water, he has no choice but to do what Jeremiah 2:13 says, to hew out his own broken cistern, which is always one that simply “won’t hold water.” We see that just as actual water gives life physically and is integral to one’s physical life, so spiritual water (the gift of holy spirit) gives life spiritually.
Consider this same parallel between water and the spirit of God in the following verses, where Jesus is speaking to a woman he met at a local well:
John 4:13 and 14
(13) Jesus answered, “Everyone who drinks this water will be thirsty again,
(14) but whoever drinks the water I give him will never thirst. Indeed, the water I give him will become in him a spring of water welling up to eternal life.”
In John 6, we find another pertinent record illustrating the analogous relationship between water and the holy spirit. I have taken a bit of literary license in summarizing verses 1-34: Jesus had been invited to a company picnic, only to discover that all 5,000 employees had forgotten their lunches. So he put up a big banner that read, “Free Food – All You Can Eat!” He then fed them delicious fish sandwiches. Later, when they got hungry again, they followed him to the other side of the lake for more free food. So Jesus, as his manner was, then began to teach them an abstract, spiritual truth that he figuratively connected to the concrete, physical acts of eating and drinking. John 6:35 is a key verse in the record, and it reads: “Then Jesus declared, ‘I am the bread of life. He who comes to me will never go hungry and he who believes in me will never be thirsty.’” Clearly, he is equating eating and drinking with believing his words. That kind of figurative language is still used today when we say that someone is “eating up” what another is saying or “drinking in” the words of a speaker.
Like his Father, Jesus is also a fountain of living waters, and he stated just that in the next chapter of John.
John 7:37-39 [Author’s translation, with punctuation and capitalization corrected]
(37) On the last and greatest day of the Feast, Jesus stood and said in a loud voice, “If anyone is thirsty, let him come to me and drink,
(38) whoever believes in me, as the Scripture has said, streams of living water will flow from within him [the Messiah].”
(39) By this he meant the spirit, whom [which] those who believed in him were later to receive. Up to that time, the spirit had not been given, since [because] Jesus had not yet been glorified.
Did Jesus stand up and mutter? No, he wanted everyone to hear his earthshaking pronouncement, so he shouted over the din of the merry revelers: “Yo! Excuse me! I am the eternal drinking fountain. If you’re thirsty, come to me and drink, by believing in me.” That is exactly the point he made in John 6 when he equated drinking with believing his words. In John 7, he proved it by referring to the Old Testament, of which he himself is the subject. The promised Messiah was the one who God, the eternal fountain, the spring of living water, sent to give drink to a dying world. And what is that “liquid” refreshment? As verse 39 emphasizes, it is the holy spirit of God, again analogously referred to as water.
The holy spirit would be given to all who believe in Jesus as Lord, but Jesus could not do this “pouring out” until after he was glorified, that is, raised from the dead and exalted to the right hand of God. At his exaltation, Jesus was given the holy spirit of God “without measure” (John 3:34 – NASB) so that he could give it to others who believed in him. For the Church, Jesus first “poured out” the holy spirit of God on the Day of Pentecost as recorded in Acts 2. In this classic verse, Peter is speaking to the amazed crowd assembled in the Temple on that historic day, and it is most significant that he also compares the gift of holy spirit to liquid:
“Exalted to the right hand of God, he [Jesus] has received from the Father the promised Holy Spirit [holy spirit] and has poured out [like water] what you now see and hear.”
When John the Baptist came as a forerunner to the Messiah, many people asked him if he were the Christ. Look closely at his reply:
John answered them all, “I baptize you with water. But [in contrast] one more powerful than I will come, the thongs of whose sandals I am not worthy to untie. He will baptize you with the Holy Spirit [no article “the”: holy spirit, the gift] and with fire.”
While John was baptizing people in the river Jordan, Jesus himself showed up, and John baptized him. Why was Jesus baptized in water? First, because he was a Jew living under the Mosaic Law, and water baptism was still pertinent to him. As Jesus said in Matthew 3:15 when John was humbly reluctant to baptize him, “Let it be so now; it is proper for us to do this to fulfill all righteousness.” That is, all of God’s requirements for the Messiah were fulfilled in Jesus, who by his baptism symbolically identified with all men’s sin and need for cleansing, and became our substitute. 
It is also significant that at the same moment when John baptized Jesus with water, God “baptized” His Son with holy spirit in the form of a dove that descended upon him. Thus, in Jesus Christ, both baptisms interfaced, showing the transition between the old and the new that would take effect on the Day of Pentecost when the Church began. Accompanied by God’s no doubt “reverb-ial” voice from heaven affirming Jesus’ identity and His love for His Son, this event marked the beginning of Jesus’ earthly ministry.
Many believe that John the Baptist was the first to baptize in water, but this is clearly not the case. If so, John would have been pretty lonely standing in the Jordan River waiting on the Israelites to come and be baptized. If the Israelites had not already known about water baptism, they would have walked away after hearing him preach and said, “What the heck was that John guy talking about, anyway? I know what ‘repent’ means, but what is this ‘baptism’ stuff?” No, as Jews, they were very familiar with water baptism, and that is why they flocked to the river. That is also why, when the priests and Levites questioned John, they did not act surprised, as if baptism were a new ritual.
Hebrews 9:10 mentions “various ceremonial washings” in the Law, and the Greek word for “washings” there is “baptisms.” God could have easily used one of several other Greek words, such as pluno, which is used of washing inanimate things; nipto, used of washing a part of the body; or louo, which means “to bathe” or “to wash the entire body.” Instead, He chose “baptisms” to refer to the Old Testament washings.
A careful reading of the Old Testament reveals various types of washings for both Israelites and proselytes to Judaism. Exodus 30:17-21 mentions the bronze basin that was placed between the door of the Tabernacle and the altar so the priests could wash their hands and feet, thus ceremonially purifying themselves so they would not die in the presence of God. Water baptism under the Law was also representative of the one baptized going down into the grave and then being re-born unto life.
According to Exodus 40:12, Aaron and his sons were brought to the Tabernacle and washed with water. When Solomon built the Temple in Jerusalem, he had a basin cast of bronze that was so large the Bible calls it “the Sea.” Scholars estimate that it held about 12,000 gallons of water and was a source of water for bathing, which was sometimes done by pouring the water over the man, and sometimes by putting it in a different container (2 Chron. 4:6).
The Mosaic Law was full of regulations about washing. There were many different things that a person could do that would make him unclean, and often the Law said that he then had to wash in water in order to re-enter the congregation. Compare Leviticus 14:9; 15:7,8,11,13,21,22,27; 16:26,28, and note the following similar verses:
Leviticus 17:15 and 16
(15) “‘Anyone, whether native-born or alien, who eats anything found dead or torn by wild animals must wash his clothes and bathe with water, and he will be ceremonially unclean till evening; then he will be clean.
(16) But if he does not wash his clothes and bathe himself, he will be held responsible.’”
In the sense of getting rid of uncleanness, bathing in water, besides being a sanitary regulation, had some typological significance. The same was true of John’s baptism – the water was symbolic of the rinsing off of sin and of showing one’s desire to enter the Kingdom of God. Also, the Levites were sprinkled with water before they started ministering in the Tabernacle (Num. 8:6 and 7). The Law even had a special water of purification that was used in certain cases of uncleanness (e.g., Num. 19).
By the time of John the Baptist, there were ritual washing pools all over Israel. Today many of these pools can be seen in the archeological excavations throughout Israel, with good examples at Qumran, New Testament Jericho, and Jerusalem itself. It is believed that the Jews of the time of Christ required a new convert to be water baptized. Hasting’s Dictionary of the Bible says, “A stranger who desired to become a Proselyte of the Covenant, or of Righteousness, i.e., in the fullest sense an Israelite, must be circumcised and baptized, and then offer a sacrifice.” It goes on to say that the person was taken “to a pool, in which he stood up to his neck in water, while the great commandments of the Law were recited to him. These he promised to keep. Then a benediction was pronounced and he plunged beneath the water, taking care to be entirely submerged.” 
Here is another telling quote regarding the prominence of ritual washings in Judaism:
Ritual immersion was important enough to the Jews that the Mishnah, which is the first section of the Talmud and collected from early oral interpretations of the Scripture, devotes an entire tractate to mikva’ot [the plural of mikveh], which were ritual immersion pools. Among other things, it describes how much water a mikveh should contain, how to stop a leak, and even places the “living water” that the mikveh contained into six grades of excellence or acceptability. The water in the mikveh was to come “by the hand of heaven” and not “by the hand of man,” so it had to be rainwater (gravity fed from rooftops was fine), springs, etc. Drawing water from cisterns to fill the mikveh was not acceptable, but in an interesting twist, since the Rabbis declared that mikveh water had the power to purify, small amounts of cistern water could be added to the “living water” to keep the mikveh full, and it was declared purified by the water already in the mikveh. The beauty of baptizing, as John did, in the Jordan River, was that there would never be any disputes about whether or not the water was Levitically acceptable. 
 Walter L. Wilson, A Dictionary of Bible Types, (Hendrickson Publishers, Inc., Peabody, MA, 1999, p. 452.)
 NIV Study Bible, note on Matthew 3:15, p. 1446.
 A Dictionary of the Bible (Hendrickson Publishers, Peabody, MA, originally published by T. & T. Clark, Edinburgh, 1898, reprinted in 1988), James Hastings, “Baptism,” Vol. 1, p. 239.
 Biblical Archaeology Review, March/April 2002, “They Are Ritual Baths,” Ronny Reich, pp. 50-55.