'Strengthen' in the Bible

So strengthen yourselves, and be valiant in heart, because your lord Saul has died, and the household of Judah has anointed me to be king over them."

be strong and strengthen thyself for our people, and for the cities of our God, and Jehovah doth that which is good in His eyes.'

And David saith unto the messenger, 'Thus dost thou say unto Joab, Let not this thing be evil in thine eyes; for thus and thus doth the sword devour; strengthen thy warfare against the city, and throw it down -- and strengthen thou him.'