Andrew Murray on Christian Unity

The bond that unites a man to his fellow-men is no less real and close than that which unites him to God: he is one with them. Grace renews not alone our relation to God but to man too. We not only learn to say "My Father," but "Our Father." Nothing would be more unnatural than that the children of a family should always meet their father separately, but never in the united expression of their desires or their love. Believers are not only members of one family, but even of one body. Just as each member of the body depends on the other, and the full action of the spirit dwelling in the body depends on the union and co-operation of all, so Christians cannot reach the full blessing God is ready to bestow through His Spirit, except as they seek and receive it in fellowship with each other. It is in the union and fellowship of believers that the Spirit can manifest His full power. It was to the hundred and twenty continuing in one place together, and praying with one accord, that the Spirit came from the throne of the glorified Lord.

Taken from the second paragraph of chapter 15 of With Christ in the School of Prayer written in 1895.