Easton's Bible Dictionary
When the apostles were brought before the council, charged with preaching the resurrection of Jesus, as a zealous Pharisee Gamaliel councelled moderation and calmness. By a reference to well-known events, he advised them to "refrain from these men." If their work or counsel was of man, it would come to nothing; but if it was of God, they could not destroy it, and therefore ought to be on their guard lest they should be "found fighting against God" (Acts 5:34-40 ). Paul was one of his disciples (22:3).
These dictionary topics are from M.G. Easton M.A., D.D., Illustrated Bible Dictionary, Third Edition, published by Thomas Nelson, 1897. Public Domain.
Easton, Matthew George. Entry for 'Gamaliel'. Easton's Bible Dictionary. https://www.studylight.org/dictionaries/eng/ebd/g/gamaliel.html. 1897.