1 Thessalonians 3:5

For this cause [because he feared that persecution might cause them to apostatize] I also, when I could no longer forbear [resuming the thought of verse 1], sent that I might know your faith, lest by any means [and Satan has many] the tempter had tempted you, and our labor should be in vain. [It is sad to lose spiritual labor, but sadder still to lose the souls which are the results of it. But we should not leave this passage without observing that if Paul had had Calvinism in mind, and had wished to assert that the elect might fall from grace and be lost despite their election, he could hardly have stated his point more clearly, for these words are addressed to those whom he has just pronounced elect.]