Chapter 1:1-8 Preaching of John the Baptist

1:1 The beginning of the gospel of Jesus Christ, the Son of God;
The beginning of the Gospel - It is with the utmost propriety that Mark begins the Gospel dispensation. It is gospel; it is God's word, and is faithful and true;
Son of God - To point out his Divine origin; and thus glancing at His miraculous conception. This was an essential character of the Messiah.

1:2 As it is written in the prophets, Behold, I send my messenger before thy face, which shall prepare thy way before thee.
Malachi, in whom we had the Old-Testament farewell, spoke very plainly (ch. 3:1) concerning John Baptist, who was to give the New-Testament -- “Behold, I send my messenger, and he shall prepare the way before me: and the Lord, whom ye seek, shall suddenly come to his temple,” (Malachi 3:1.).

1:3 The voice of one crying in the wilderness, Prepare ye the way of the Lord, make his paths straight.
The voice of one crying - See on Matthew 3:1-3;

1:4 John did baptize in the wilderness, and preach the baptism of repentance for the remission of sins.
John - The original name is nearly lost in the Greek Ιωαννης, and in the Latin Johannes, and almost totally so in the English John. The original name is יהוחנן Yehochanan, compounded of חנן יהוה Yehovah chanan, the grace or mercy of Jehovah: a most proper and significant name for the forerunner of the God of All Grace. 

It was John's business 

---to proclaim the Gospel of the grace of God, 

---and to point out that Lamb or sacrifice of God which takes away the sin of the world.
For the remission of sins - Or, toward the remission - εις αφεσιν . They were to repent, and be baptized in reference to the remission of sins.
He preached repentance, in order to it; he told people that there must be a renovation of their hearts and a reformation of their lives, that they must forsake their sins and turn to God, and upon those terms and no other, their sins should be forgiven.

1:5 And there went out unto him all the land of Judaea, and they of Jerusalem, and were all baptized of him in the river of Jordan, confessing their sins.
Confessing their sins - It was an invariable custom among the Jews to admit no proselyte to baptism, till he had, in the most solemn manner, declared that he forever had renounced all idolatrous worship, all heathenish superstitions, and promised an entire and unreserved submission to the law of Moses.

1:6 And John was clothed with camel's hair, and with a girdle of a skin about his loins; and he did eat locusts and wild honey;
John was clothed, etc. - See the note on Matthew 3:4.

1:7 And preached, saying, There cometh one mightier than I after me, the latchet of whose shoes I am not worthy to stoop down and unloose.
He preached Christ, and directed his hearers to expect Him speedily to appear, and to expect great things from Him.

1:8 I indeed have baptized you with water: but He shall baptize you with the Holy Ghost.
As if he had said: 

This baptism is not to be rested in; 

it is only an emblem of that which you must receive from Him who is mightier than I. 

It is He only who can communicate the Holy Spirit; and water baptism is nothing, but as it points out, and leads to, the baptism of the Holy Ghost. 

--They shall be baptized with the Holy Ghost, 

--shall be purified by His graces, 

--and refreshed by His comforts.