Charles H. Spurgeon on Psalms 133:1

To dwell is a word of residence, and abode, and continuation. There is also pertaining to the love and concord of brethren a perseverance and persistency in it; not only to be together, or to come together, or to meet together for some certain time; but to dwell together in unity, this is which is here so extolled and commended unto us. It seems to be no such great matter, nor to carry any such great difficulty in it, for men to command themselves to some expressions of peace and friendship for some short space of time (though there are many now and then who are hardly able to do that); but to hold out in it, and to continue so long, this endurance is almost impossible to them. Yet this is that which is required of them as Christians and as "brethren" one to another, even to "dwell together in unity; "to follow peace, and love, and concord, and mutual agreement, not only upon some occasional meetings, but all along the whole course of their lives, while they converse and live together. —Thomas Horton.