Anointing
If you were just east of Jericho around 27 A.D., you might have found a wild-looking man wearing sackcloth, preaching, and immersing people in the Jordan River. Perhaps there, you would have overheard this snippet of conversation:
"I need to be baptized by you, and do you come to me?" But Jesus answered him, "Let it be so now, for thus it is fitting for us to fulfill all righteousness." Matthew 3:14–15
Why should Jesus be immersed in this way?
The Law often used water immersion to denote a cleansing of sin before presentation before God. For instance, in 1 Kings 7:23 we read:
Then he made the sea of cast metal. It was round, ten cubits from brim to brim, and five cubits high, and a line of thirty cubits measured its circumference.
The priests used this sea to wash before approaching the Altar of the Lord:
You shall also make a basin of bronze, with its stand of bronze, for washing. You shall put it between the tent of meeting and the altar, and you shall put water in it, with which Aaron and his sons shall wash their hands and their feet. When they go into the tent of meeting, or when they come near the altar to minister, to burn a food offering to the LORD, they shall wash with water, so that they may not die. Exodus 30:18–20
Washing was not a way to remit or cover sins but rather to become ceremonially clean before appearing before the Lord.
A mikvah in the Hebrew Bible is a gathering or collection of water. The word came to refer to a pool of water used for ceremonial cleansing. One who is impure or ceremonially unclean before immersion will be pure or ceremonially clean after immersion in a mikvah. ... Later, ritual immersion—baptism—became part of a proselyte's conversion to Judaism.[1]
Immersion and washing were not restricted to the Temple and its Courts. In Jesus' time, Jews used hundreds of Mikvah baths throughout Jerusalem (and other major cities), such as the one shown below, for ceremonial cleansing.
Observant Jews would step into the pools of water to wash before visiting the Temple—and perhaps before prayer or undertaking other sacred events. Washing through immersion, then, was an essential part of Jewish culture, and John's baptism would not have seemed so out of place.
This washing for purification was also a part of consecration:
You shall consecrate them, that they may be most holy. Exodus 30:29
So, the process of washing contains the ideas of setting apart (or making holy) and ceremonial cleansing. Hence, the baptism of Jesus—at its most minimal—would mark his ceremonial cleansing and separation for the Lord's work.
However, the events of Jesus' baptism go far beyond the kind of consecration to service found in immersion.
Then he consented. And when Jesus was baptized, immediately he went up from the water, and behold, the heavens were opened to him, and he saw the Spirit of God descending like a dove and coming to rest on him; and behold, a voice from heaven said, "This is my beloved Son, with whom I am well pleased." Matthew 3:13–17
This annunciation from the Father and the Spirit's descent on Jesus is parallel to a theocratic anointing from the Tanakh (or Old Testament). The Spirit was placed on leaders throughout Israel's history to help them fulfill a specific purpose within God's plan.
Moses:
And I will come down and talk with you there. And I will take some of the Spirit that is on you and put it on them, and they shall bear the burden of the people with you, so that you may not bear it yourself alone. Numbers 11:17
Joshua:
So the LORD said to Moses, "Take Joshua the son of Nun, a man in whom is the Spirit, and lay your hand on him. Numbers 27:18
Othniel:
The Spirit of the LORD was upon him, and he judged Israel. Judges 3:10
Samson:
And the Spirit of the LORD began to stir him in Mahaneh-dan, between Zorah and Eshtaol. Judges 12:25
Saul:
Then the Spirit of the LORD will rush upon you, and you will prophesy with them and be turned into another man. 1 Samuel 10:6
Saul’s loss of the Spirit:
Now the Spirit of the LORD departed from Saul, and a harmful spirit from the LORD tormented him. 1 Samuel 16:14
David:
Then Samuel took the horn of oil and anointed him in the midst of his brothers. And the Spirit of the LORD rushed upon David from that day forward. And Samuel rose up and went to Ramah. 1 Samuel 16:13
This theocratic anointing among the kings of Israel seems to have ended with Solomon, being transferred to the prophets. This "descending of the Spirit" on Jesus was not new in Israel's history.
Jesus' theocratic anointing is a return to the time of David. It is not invalidated by Israel's temporary rejection of Jesus any more than David's rejection invalidated God's anointing over him.
Jesus' baptism goes far beyond simply opening his ministry or consecration for ministry. Jesus' baptism is his consecration to carry God's plan forward and his kingship over his people, Israel.
[1] Got Questions Ministries, Got Questions? Bible Questions Answered, vol. 2 (Bellingham, WA: Faithlife, 2014).