Note 2 at Acts 5:39: This counsel of Gamaliel was true in this instance and definitely worked to the apostles advantage, but it is not a truth that is applicable in all situations.

First, not every purpose that is not of God, fails. Ultimately, everything that is not of God will be destroyed at His coming, but until then, many ungodly causes prosper. In direct opposition to Gamaliel's advice, the Lord gave commands to his ministers to counter errors in His church (Ti. 1:11; Rev. 2:14-15, 20).

Secondly, not every cause of God succeeds. Ultimately, God's will will prevail but at the present, many things are happening outside of God's will. It is not God's will that anyone should perish (2 Pet. 3:9), but people are perishing because God has given us the freedom of choice (Dt. 30:19). It is God's will for us to be healed (Isa. 53:5; Mt. 8:17; 1 Pet. 2:24; 3 Jn. 2), but not every one gets healed.

God hates the murdering of children, and yet millions of unborn children are being killed every year. We cannot adopt the attitude that Gamaliel put forth here to simply be passive and believe that those things which are not of God will fail. We have to stand up for what is right and oppose that which is wrong.