Matthew Poole and continuators on Acts 12:4

4 And when he had apprehended him, he put him in prison, and delivered him to four quaternions of soldiers to keep him, intending after Easter to bring him forth to the people.

There were sixteen Soldiers appointed to keep Peter; the Romans using four Soldiers at a time to keep Centry, and the Iews dividing their nights into four watches, there were enough to relieve the other, and to set a new watch as often as was required for every night; of which four at a time, two were with the prisoner, and perhaps for the greater security, bound with the same chain; and two did always stand at the door or gate; and this they might the rather do, out of great caution, having heard what Miracles Peter did; and that he had been delivered by an Angel out of prison, Chap. 5.19.

That day in which the Paschal Lamb was eat, on which the Iews would put none to death, that they might not eclipse the joy of that day.

To do with him what they would, leaving him to their mercy, or rather cruelty.

Marginal references: John 21.18.