For the gifts and the calling of God are irrevocable. Romans 11:29
Study and be eager and do your utmost to present yourself to God approved (tested by trial), a workman who has no cause to be ashamed, correctly analyzing and accurately dividing [rightly handling and skillfully teaching] the Word of Truth. 2 Timothy 2:15 AMP
Therefore I remind you to stir up the gift of God which is in you...
2 Timothy 1:6