Deprive not yourselves of the blessing of invoking God together with one accord, and receiving some sound doctrine and good exhortation, to make you hold on in the right path. For though each one can and should also pray to God in secret, and having retired apart, and though each can read in his own house—notwithstanding well-pleasing to God is the sacrifice of assembling ourselves to pray to him with one mouth, and offer up to him the solemn homage both of our souls and of our bodies.
And it were much to be desired, that we could do so before the world; but since by the malice and tyranny of men we are forestalled of this privilege, the least we can do is to praise God along with his people, as the scripture exhorteth us. To do this, small flocks group together here and there, till in the end the whole body of the church be collected in the kingdom of heaven. – Calvin
Why, If You’re a Christian, You Ought to Be In Worship