'Be Strong' in the Bible

Now therefore let your hands be strong, and be ye valiant, for Saul your lord is dead, and also the house of Judah have anointed me king over them.

And Ahithophel said to Absalom, Go in to thy father's concubines that he has left to keep the house, and all Israel will hear that thou are abhorred by thy father. Then the hands of all who are with thee will be strong.