That their hearts might be comforted, being knit together in love, and unto all riches of the full assurance of understanding, to the acknowledgment of the mystery of God, and of the Father, and of Christ; (2:2)

--1 Thessalonians--

For our gospel came not unto you in word only, but also in power, and in the Holy Ghost, and in much assurance; as ye know what manner of men we were among you for your sake. (1:5)