If the dough rises, however, you can be sure there is living yeast in it. Risen dough is evidence that there is life in the yeast. James said something similar; “You see that a person is justified by works and not by faith alone.” (James 2:24, NASB 2020)

This verse closes out Paul’s lengthy parenthetical comment. It is a bit difficult, and the Greek syntax allows for three potential ways of understanding Paul’s meaning. The best of these, which fits well with his urging them to remain strong despite the difficulties Paul is facing, has a parallel in Philippians 1:27–30

The Spirit of God, the self-same Spirit that raised Christ from the dead (see Romans 8:11), has been given to us as a down-payment, or deposit in earnest, guaranteeing our inheritance.