He doesn't call the equipped but he equips the called. Whatever He commands us to do He gives us the ability to do. He speaks us into being like HIM. We are created FOR good works. Through His Spirit good fruit is produced as unto righteousness.
Hebrews 2:14 ESV
Since therefore the children share in flesh and blood, he himself likewise partook of the same things, that through death he might destroy the one who has the power of death, that is, the devil,
How can a man preach if he does not get his message fresh from God in the prayer closet? How can he preach without having his faith quickened, his vision cleared, and his heart warmed by his solitude with God?