'Add' in the Bible

Ho Ariel, Ariel, the city where David encamped! add ye year to year; let the feasts come round:

Woe to the rebellious children, saith Jehovah, that take counsel, but not of me; and that make a league, but not of my Spirit, that they may add sin to sin,

Go, and say to Hezekiah, Thus saith Jehovah, the God of David thy father, I have heard thy prayer, I have seen thy tears: behold, I will add unto thy days fifteen years.