Tertullian

For when they shall say, `Peace, 'and `All things are safe, 'then sudden destruction shall come upon them." Again, in the second epistle he addresses them with even greater earnestness: "Now I beseech you, brethren, by the coming of our Lord Jesus Christ, and by our gathering together unto Him, that ye be not soon shaken in mind, nor be troubled, either by spirit, or by word," that is, the word of false prophets, "or by letter," that is, the letter of false apostles, "as if from us, as that the day of the Lord is at hand.