Albert Barnes Commentary Acts 12:14

"And when she knew Peter`s voice, she opened not the gate for joy, but ran in, and told that Peter stood before the gate." — Acts 12:14 (ASV)

She opened not the gate. At this time of night, and in these circumstances, the door would be fastened. Christians were doubtless alarmed by the death of James, and the imprisonment of Peter, and they would take all possible precautions for their own safety.

For gladness. In her joy, she hastened to inform those who were assembled of the safety of Peter.

(The word "gate" here can also be rendered "porch".)