A.T. Robertson Commentary Acts 4:16

"saying, What shall we do to these men? for that indeed a notable miracle hath been wrought through them, is manifest to all that dwell in Jerusalem; and we cannot deny it." — Acts 4:16 (ASV)

What shall we do? (Τ ποιησωμεν). Deliberative aorist active subjunctive (ingressive and urgent aorist).

Notable miracle (γνωστον σημειον). Or sign. It was useless to deny it with the man there.

We cannot deny it (ου δυναμεθα αρνεισθα). That is, it will do no good.