Acts 5:38 And now I say to you, keep away from these men and let them alone; for if this plan or this work is of men, it will come to nothing;
Gamaliel was a very wise Pharisee who was watching the acts of the apostles closely. His advice was sound advice.
He told the leaders to leave the apostle alone and if it was not the truth it would all fizzle out; natural selection if you will.
What we see today is how this same Word has continued to be with us and lead us for thousands of years. It has not fizzled out because it is the truth!