John Gill Commentary Mark 14:24

"And he said unto them, This is my blood of the covenant, which is poured out for many." — Mark 14:24 (ASV)

And he said to them: Not after they had drank of it, but before, and as he gave it to them:

this is my blood of the New Testament, which is shed for many;

in Matthew it is added, "for the remission of sins"; (See Gill on Matthew 26:28).