'Lost Sheep' in the Bible

I have wandered like a lost sheep; seek your servant, because I do not forget your commands.

My people have become lost sheep, their shepherds have caused them to go astray. They led them away [to the] mountains. From mountain to hill they have gone, they have forgotten their resting place.

but go instead to the lost sheep of the house of Israel.

But he answered [and] said, "I was not sent except to the lost sheep of the house of Israel."