'Be Strong' in the Bible

And the fourth kingdom shall be strong as iron: since iron breaks in pieces and subdues all things: and as iron that breaks all these, shall it break in pieces and bruise.

And said, O man greatly beloved, fear not: peace be unto you, be strong, yea, be strong. And when he had spoken unto me, I was strengthened, and said, Let my lord speak; for you have strengthened me.

And the king of the south shall be strong, and one of his princes; and he shall be strong above him, and have dominion; his dominion shall be a great dominion.

And such as do wickedly against the covenant shall he corrupt by flattery: but the people that do know their God shall be strong, and take action.