The strength that God gives to His Josephs is real strength; it is not a boasted valor, a fiction, a thing of which men talk but which ends in smoke; it is true--divine strength.
Why does Joseph stand against temptation? Because God enables him. There is nothing that we can do without the power of God. All true strength comes from "the Mighty One of Jacob." Notice in what a blessedly familiar way God gives this strength to Joseph--"His arms were made agile by the hands of the Mighty One of Jacob." God is represented as putting His hands on Joseph's hands, placing His arms on Joseph's arms. Just as a father teaches his children, so the Lord teaches them that fear Him. He puts His arms upon them. Marvelous condescension! God Almighty, Eternal, Omnipotent, stoops from His throne and lays His hand upon the child's hand, stretching His arm upon the arm of Joseph, that he may be made strong!
This strength was also covenant strength, for it is ascribed to "the Mighty One of Jacob." Now, wherever you read of the God of Jacob in the Bible, you should remember the covenant with Jacob. Christians love to think of God's covenant. All the power, all the grace, all the blessings, all the mercies, all the comforts, all the things we have flow to us from the fountainhead, through the covenant. If there were no covenant, then we should fail indeed; for all grace proceeds from it, as light and heat from the sun. No angels ascend or descend except by the ladder that Jacob saw, at the top of which stood a covenant God. Christian, it may be that the archers have sorely grieved you and shot at you and wounded you, but still your bow remains unmoved. Be sure, then, to ascribe all the glory to Jacob's God.