Was there baptism in the Old Testament?
Yes. sort of.
There were a few incidents in the Old Testament that could be regarded as being types of baptisms. There was Moses and the Israelite's crossing of the Red Sea, and Joshua's and the Israelites' crossing of the river Jordan. And, so was there Elijah who told the leper Naaman to go and dip himself in the river Jordan to get healed.
Consequently, three times "baptisms" in the river Jordan occurred. The Israelites crossed the river Jordan on their way to the promised land, Naaman the Leper got healed from his leprosy when dipping himself in the river Jordan, and John baptized troubled sinners in the same river Jordan.
2 Cor 13:1 (NIV) “Every matter must be established by the testimony of two or three witnesses.”
Jesus said that John was Elijah.
Mat 11:13,14 (NIV) "... all the Prophets and the Law prophesied until John. And if you are willing to accept it, he is the Elijah who was to come".
Mat 17:10-13 (NIV)10 The disciples asked him, “Why then do the teachers of the law say that Elijah must come first?” Jesus replied, “To be sure, Elijah comes and will restore all things. But I tell you, Elijah has already come, and they did not recognize him, but have done to him everything they wished. In the same way the Son of Man is going to suffer at their hands.” Then the disciples understood that he was talking to them about John the Baptist".
But John himself said that he was not Elijah.
John 1:19-23 (NIV) Now this was John’s testimony when the Jewish leaders in Jerusalem sent priests and Levites to ask him who he was. He did not fail to confess, but confessed freely, “I am not the Messiah.”
They asked him, “Then who are you? Are you Elijah?” He said, “I am not.”
“Are you the Prophet?” He answered, “No.” Finally they said, “Who are you? Give us an answer to take back to those who sent us. What do you say about yourself?” John replied in the words of Isaiah the prophet, “I am the voice of one calling in the wilderness, ‘Make straight the way for the Lord.’”
This is interesting. Here we see a thesis and an antithesis. It is possible that the synthesis of this paradox is that Jesus equated John's baptism with Elijah's baptism, rather than equating him with Elijah, as a person; thus implying that John was not Elijah reincarnated.
"Elijah's baptism" took place in the story about the foreigner with leprosy in 2 Kings 5. The guy's name was Naaman.
2 Kings 5:8-14 (NIV) When Elisha the man of God heard that the king of Israel had torn his robes, he sent him this message: “Why have you torn your robes? Have the man come to me and he will know that there is a prophet in Israel.” So Naaman went with his horses and chariots and stopped at the door of Elisha’s house. Elisha sent a messenger to say to him, “Go, wash yourself seven times in the Jordan, and your flesh will be restored and you will be cleansed.”
But Naaman went away angry and said, “I thought that he would surely come out to me and stand and call on the name of the Lord his God, wave his hand over the spot and cure me of my leprosy. Are not Abana and Pharpar, the rivers of Damascus, better than all the waters of Israel? Couldn’t I wash in them and be cleansed?” So he turned and went off in a rage.
Naaman’s servants went to him and said, “My father, if the prophet had told you to do some great thing, would you not have done it? How much more, then, when he tells you, ‘Wash and be cleansed’!” So he went down and dipped himself in the Jordan seven times, as the man of God had told him, and his flesh was restored and became clean like that of a young boy.