“And now I say to you, Refrain from these men, and let them alone, for if this counsel or this work be of men, it will be overthrown, but if it is of God, you will not be able to overthrow them; lest haply you be found even to be fighting against God.”
So Gamaliel advised that the men be left alone in case their activities were of God, and pointed out that if they were of God, to fight against them would be to fight against God..