If we understand that in power and in the Holy Spirit and with full conviction
describes the work in the Thessalonian believers, then it leads us to understand in power
as the divine power that worked in the Thessalonians, causing them to accept the gospel message and put their trust in Jesus Christ.
5 because our gospel came to you not only in word, but also in power and in the Holy Spirit and with full conviction. You know what kind of men we proved to be among you for your sake.