Acts 12:10

And when they were past the first and the second guard, they came unto the iron gate that leadeth into the city; which opened to them of its own accord: and they went out, and passed on through one street; and straightway the angel departed from him.

That great iron gate stands for death in this allegory. No man is safe from the fury of the evil one until death has ended his probation. To leave off following the Lord before death is to die in Satan's dominion and under his control. That is why an apostle said, "Blessed are the dead who die in the Lord" (Revelation 14:13). Peter did not leave off following the angel until the iron gate opened and closed behind him. That gate took twenty-five men to open and close it. It was the gate of a fortress so impregnable that soldiers were not even stationed to guard it. It did not need it. They just locked it and left it, unlocking it only as needed, and leaving it unattended the rest of the time.

Which opened unto them of its own accord ... The gate of death opened for Stephen who saw Jesus standing on the right hand of God (7:56); and every true Christian may expect the Lord to bless him in the hour of death. Its iron gates will open of their own accord (Psalms 23).

It should be noted that Peter was destined to go through that iron gate in one of two ways. Had he passed through it the next morning it would have been in custody of Herod's soldiers on the way to his execution; but to go through it with an angel of God was a far different thing. So also, every Christian and every man will pass through the iron gate of death; but for some, alas, it will be the gate to everlasting sorrow; and for others it will be the gate of everlasting joy.