John Gill Commentary Mark 14:42

"Arise, let us be going: behold, he that betrayeth me is at hand." — Mark 14:42 (ASV)

Rise up let us go
To meet the enemy and the danger; for there is no escaping;

lo, he that betrays me is at hand ;
Judas, that he had hinted at supper should betray him, was now about doing it; and was just now coming upon him, in order to deliver him into the hands of the Jews, and the Roman band of soldiers; (See Gill on Matthew 26:46).