'Be Strong' in the Bible

He will keep the feet of his saints but the wicked shall keep silence in darkness. For in his own might shall no man be strong.

Be strong, and quit yourselves like men, O ye Philistines, that ye be not servants unto the Hebrews, as they have been to you: quit yourselves like men, and fight.

And David will be strong upon him of the rovers with a sling and with a stone, and he will strike him of the rovers and kill him, and no sword in David's hand.

And Saul said to David, Here is my oldest daughter Merab, whom I will give you for your wife: only be strong for me, fighting in the Lord's wars. For Saul said, Let it not be through me that his fate comes to him, but through the Philistines.