John Mark
Mark 3:19ESV·traditional attribution

and Judas Iscariot, who betrayed him.

Matthew Henry Presbyterian @wholebiblehenry

In these verses, we have, I. The choice Christ made of the twelve apostles to be his constant followers and attendants, and to be sent abroad as there was occasion, to preach the gospel. Observe, 1. The introduction to this call or promotion of disciples; He goes up into a mountain, and his errand thither was to pray.

Commenting on Mark 3:13-21

John Gill Reformed Baptist @doctorgill

And the multitude coming together again,.... Either the multitude that were about the door of this house; insomuch that there was no room about, nor any coming near it, Mar 2:2, or the multitude that came from different parts, and had thronged about him at the sea side, before he went up into the mountain: these understanding that he was come down from thence, and...

Albert Barnes Presbyterian @notesbybarnes

Verse 19. (1) "they went into a home" or, "home"