'Mayest' in the Bible

Only be strong and very courageous, that thou mayest take heed to do according to all the law that Moses my servant commanded thee. Turn not from it to the right or to the left, that thou mayest prosper whithersoever thou goest.

This book of the law shall not depart from thy mouth; and thou shalt meditate upon it day and night, that thou mayest take heed to do according to all that is written therein; for then shalt thou have good success in thy ways, and then shalt thou prosper.