'Fold' in the Bible

I have other sheep [beside these] that are not of this fold. I must bring those also, and they will listen to My voice and pay attention to My call, and they will become one flock with one Shepherd.

But you do not believe Me [so you do not trust and follow Me] because you are not My sheep.

shepherd and guide and protect the flock of God among you, exercising oversight not under compulsion, but voluntarily, according to the will of God; and not [motivated] for shameful gain, but with wholehearted enthusiasm;