Gave their witness (apedidoun to marturion). Imperfect active of apodidōmi, old verb to give back, to pay back a debt (Luk 7:42), but a late omega form instead of the usual apedidosan. They kept on giving their witness with power after the answer to their prayer (Act 4:31).
Of the resurrection (tēs anastaseōs). It was on this issue that the Sadducees had arrested them (Act 4:1-3).