2 Samuel 3:21

And Abner said unto David, I will arise and go, and will gather all Israel unto my lord the king that they may make a league with thee, acknowledging him as the chosen king of Jehovah, through whom, as His instrument, the Lord Himself would rule over His people, and that thou mayest reign over all that thine heart desireth, over the entire people of God. And David sent Abner away; and he went in peace, regarded by David as a true friend to his cause. Even the adversaries of God and Christ are often instrumental in carrying out the counsel of God and in furthering the cause of Christ. And many a person who first strongly opposed the Lord has been brought to a better understanding and has embraced the good cause.