Adam Clarke on 2 Timothy 1:9

Who hath saved us - From sin; the spirit of bondage, and all tormenting fear. This is the design of the Gospel.

And called us with a holy calling - Invited us to holiness and comfort here; and to eternal glory hereafter.

Not according to our works - We have not deserved any part of the good we have received; and can never merit one moment of the exceeding great and eternal weight of glory which is promised. See the notes on the parallel passages.

Before the world began - Προ χρονων αιωνιων. Before the Mosaic dispensation took place, God purposed the salvation of the Gentiles by Christ Jesus; and the Mosaic dispensation was intended only as the introducer of the Gospel. The law was our schoolmaster unto Christ, Gal 3:24. See the parallel places, and the notes there.