Acts 5:35

Ye men of Israel It has been remarked upon the frequent occurrence of this and similar formulæ in the introduction of speeches in the Acts, that they are evidence that the speeches themselves are the composition of the writer of the book, and are only his own thoughts of the matter put into the mouths of the various speakers. After what has been said on the character of all the speeches, that they make no attempt to set before us all that was said on each occasion, but only the substance of what St Luke had received from eye and ear-witnesses, it can in no wise detract from the substantial veracity of all that is reported, if we find the compiler of the Acts, who was himself a Greek, giving the usual Greek form of introduction to the speeches of which he has shewn so often that he intends to supply only an outline.

take heed to yourselves The phrase implies that thought is required before any action be taken. It is not, as the English words are sometimes taken to be, a warning against some danger which was impending.