'Be Strong' in the Bible

The fourth kingdom shall be strong as iron, because iron breaks in pieces and subdues all things; and as iron that crushes all these, shall it break in pieces and crush.

He said, "Greatly beloved man, don't be afraid: peace be to you, be strong, yes, be strong." When he spoke to me, I was strengthened, and said, "Let my lord speak; for you have strengthened me."

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.

Such as do wickedly against the covenant shall he pervert by flatteries; but the people who know their God shall be strong, and do [exploits].