Mark 1:5

And there went out unto him all the land of Judea,.... The people of the land, a great number of them:

and they of Jerusalem; the inhabitants of Jerusalem, hearing of this new preacher, the new doctrine that he taught, and the new ordinance that he administered:

and were all baptized of him in the river Jordan, confessing their sins; that is, as many of them as were brought to a sight and sense of their sins, and made a confession of them, these he baptized, or immersed, in the river Jordan; for certain it is, that there were many of the Pharisees and Sadducees who came, whom he rejected;

[See comments on Matthew 3:5],

[See comments on Matthew 3:6],

[See comments on Matthew 3:7].