Charles Ellicott Commentary Mark 1:5

"And there went out unto him all the country of Judaea, and all they of Jerusalem; And they were baptized of him in the river Jordan, confessing their sins." — Mark 1:5 (ASV)

There went out unto him...—See Note on Matthew 3:5. Note St. Mark’s use of the term in the river of Jordan, as writing for those who were not familiar with the topography of Palestine.