Pseudo-Chrysostom
Catena Aurea · Matthäusevangelium 6
Therefore when thou doest thine alms, do not sound a trumpet before thee, as the hypocrites do in the synagogues and in the streets, that they may have glory of men. Verily I say unto you, They have their reward. But when thou doest alms, let not thy left hand know what thy right hand doeth: That thine alms may be in secret: and thy Father which seeth in secret Himself shall reward thee openly.
The trumpet stands for every act or word that tends to a display of our works; for instance, to do alms if we know that some other person is looking on, or at the request of another, or to a person of such condition that he may make us return; and unless in such cases not to do them. Yea, even if in some secret place they are done with intent to be thought praiseworthy, then is the trumpet sounded.