Note 2 at Ac 5:19: It is interesting that the angel freed the apostles at night. This could have been done in broad daylight for everyone to see, but it wasn't. This is consistent with many miraculous occurrences in the Bible (see note 1 at Mr 16:9). The Lord does enough miracles that no one has an excuse to reject Him, but most of His dealings with us are in ways noticed only by those who already believe. It is faith that pleases the Lord (Heb 11:6), not sight (2Co 5:7).

Note 3 at Ac 5:19: This is the first time in Scripture that anyone was miraculously delivered from prison by an angel. Joseph and Jeremiah were imprisoned without the Lord providing them with a miraculous escape. Instead, they were vindicated and released.

Later in the book of Acts (Ac 12:1-19), Peter was also released in a similarly miraculous fashion. However, the Apostle Paul spent years in prison (Ac 21-28). As Paul later explained in Php 1:12-14, his imprisonment gave him an all-expense paid trip to Rome to witness to Caesar himself.