John Gill Commentary Mark 14:7

"For ye have the poor always with you, and whensoever ye will ye can do them good: but me ye have not always." — Mark 14:7 (ASV)

For you have the poor with you always
(See Gill on Matthew 26:11);

and whenever you will you may do them good ;
by feeding them when hungry, clothing them when naked, and supplying them with the necessaries of life:

but me you have not always ;
meaning, with respect to his bodily presence, which, in a short time, would be removed from them, and they would have no opportunity of showing him any such outward respect personally; (See Gill on Matthew 26:11).