'Mayest' in the Bible

And Abner said to David, I will arise and go, and will gather all Israel to my lord the king, that they may make a covenant with thee, and that thou mayest reign over all that thy heart desires. And David sent Abner away; and he went in peace.

but if thou return to the city, and say to Absalom, I will be thy servant, O king; as I have been thy father's servant hitherto, so now will I be thy servant; then mayest thou for me defeat the counsel of Ahithophel.