Mark 1:6

And John was clothed with camel's hair, and had a leathern girdle about his loins, and did eat locusts and wild honey. And he preached, saying, There cometh after me he that is mightier than I, the latchet of whose shoes I am not worthy to stoop down and unloose. I baptized you in water; but he shall baptize you in the Holy Spirit.

These verses conclude Mark's account of the ministry of John the Baptist, an account which is shorter than Matthew's, omitting such important details as John's proclamation of the kingdom of heaven being near at hand and the insistence of the Pharisees that fleshly descent from Abraham was all they needed (Matthew 3:1-12). John's prophecy of the rejection of national Israel was also omitted.

The clothing and diet of John were cited as fulfilling the typical characteristics of Elijah. There is no need to understand "locusts and wild honey" otherwise than in their ordinary sense.

Mightier than I ... John the Baptist is unique among the world's great men in this view of himself as inferior to his successor. This is all the more remarkable in view of their close kinship and of their being approximately the same age.

Baptize you in the Holy Spirit ... is a reference to the Spirit which Jesus would pour out on earth. The baptism of the Holy Spirit is variously understood as: (1) the experience on Pentecost (Acts 2:1-4), (2) an event like that in the home of Cornelius (Acts 10:44-48), (3) the miraculous endowment of the apostles (Acts 8:18), or (4) the guidance of the church throughout the ages by God's Spirit through the word, including the indwelling earnest. Although including the latter, the baptism in view here exceeds it, affecting all mankind. Significantly, it is a promise of what Christ would do and not a commandment men were to obey. This is one of seven baptisms mentioned in the New Testament, the others being: (1) the baptism unto Moses (1 Corinthians 10:2), (2) that of sufferings (Mark 10:38,39), (3) that for the dead (1 Corinthians 15:29), (4) that of fire (Matthew 3:11), (5) that of John the Baptist (Acts 19:3), and (6) that of the great commission (Mark 16:15,16; Matthew 28:18-20).

For fuller discussion of the ministry of John the Baptist, as related by Matthew, see Commentary on Matthew, (Matthew 3:1-14) pp. 23-31.