Adam Clarke

Stir up the gift of God, which is in thee - The gift which Timothy had received was the Holy Spirit; and through him, a particular power to preach and defend the truth. This gift is represented here, under the notion of a fire, which, if it be not frequently stirred up, and fresh fuel added to it, will go out. This is the precise idea which the apostle had in his mind; hence the term αναζωπυρειν, which signifies to stir up the fire; to add fresh fuel to it. From this it plainly appears, that if Timothy had not continued to be a daily worker with God, he would have received the grace of God in vain. The Latins have a similar metaphor, excitare igniculos ingenii, to stir up the sparks of genius. By the putting on of my hands - See on Ti1 4:14 (note).