John Gill

Wherefore ye be witnesses unto yourselves,.... Or "against yourselves", as the Syriac reads; for what they said was a plain acknowledgment, and a full confession, what their fathers had done, and whose offspring they were; and from whom better things were not to be expected; since they were their fathers' own children, and of the same temper and disposition with them: that ye are the children of them that killed the prophets. They plainly owned, that their fathers killed the prophets, and that they descended from them; though they meant not so much to reproach, their ancestors, as to give themselves a greater character; yet it did not with those, that knew them; not with our Lord: for as their own words testified against them, that they were a seed of evildoers; their practices showed them to be of the same spirit and principles with their progenitors.