John the Baptist’s mission included a very important act in the life and death of Jesus. He was to fulfil the Law which required a sacrifice to be washed by a priest before it was offered.

John the Baptist’s father was a priest named Zacharias, of the course of Abia while his mother was of the daughters of Aaron. John was thus also of the priestly lineage. (Luke 1:5, 57, 59-60).

Jesus chose John the Baptist to do his part as a priest to fulfill the righteousness of the Law. Jesus, before He was offered as our sacrifice on the cross as the sinless Lamb of God and sacrifice for our sins, asked John the Baptist to wash Him by water baptism.

The priests, Aaron’s sons, washed the sacrifices before they were offered.

"And he shall kill the bullock before the LORD... And the priests, Aaron's sons, shall lay the parts, the head, and the fat, in order upon the wood that is on the fire which is upon the altar: but his inwards and his legs shall he wash in water: and the priest shall burn all on the altar, to be a burnt sacrifice, an offering made by fire, of a sweet savour unto the LORD." - Leviticus 1:5a, 8-9 KJV

John the Baptist called Jesus, “the Lamb of God.” He came as a sacrifice for our sins.

"The next day John seeth Jesus coming unto him, and saith, Behold the Lamb of God, which taketh away the sin of the world." - John 1:29 KJV

"And looking upon Jesus as he walked, he saith, Behold the Lamb of God!" - John 1:36 KJV

"Then cometh Jesus from Galilee to Jordan unto John, to be baptized of him. But John forbad him, saying, I have need to be baptized of thee, and comest thou to me?

“And Jesus answering said unto him, Suffer [allow] it to be so now: for thus it becometh us to fulfil all righteousness. Then he suffered him." - Matthew 3:13-15 KJV

Christ’s sacrifice - an offering of a sweet savour.

"And walk in love, as Christ also hath loved us, and hath given himself for us an offering and a sacrifice to God for a sweetsmelling savour." - Ephesians 5:2 KJV