John Calvin Commentary Matthew 6:3

"But when thou doest alms, let not thy left hand know what thy right hand doeth:" — Matthew 6:3 (ASV)

Let not your left hand know. By this expression He means that we ought to be satisfied with having God as our only witness, and to be so earnestly desirous to obey Him that we shall not be carried away by any vanity. It frequently happens that people sacrifice to themselves rather than to God. Christ therefore wishes that we should not be distracted by indirect thoughts, but go straight to this objective, that we may serve God with a pure conscience.