'Able' in the Bible

Now when all the Moabites heard that the kings were come up to fight against them, they gathered themselves together, all that were able to put on armor, and upward, and stood on the border.

Now therefore, I pray thee, give pledges to my master the king of Assyria, and I will give thee two thousand horses, if thou be able on thy part to set riders upon them.

Thus saith the king, Let not Hezekiah deceive you; for he will not be able to deliver you out of his hand: