'Able' in the Bible

And the men of Beth-shemesh said, Who is able to stand before Jehovah, this holy God? and to whom shall he go up from us?

If he be able to fight with me, and kill me, then will we be your servants; but if I prevail against him, and kill him, then shall ye be our servants, and serve us.

And Saul said to David, Thou art not able to go against this Philistine to fight with him; for thou art but a youth, and he a man of war from his youth.