Matthew Henry's Concise Commentary

4:9-12 Surely he has more satisfaction in life, who labours hard to maintain those he loves, than the miser has in his toil. In all things union tends to success and safety, but above all, the union of Christians. They assist each other by encouragement, or friendly reproof. They warm each other's hearts while they converse together of the love of Christ, or join in singing his praises. Then let us improve our opportunities of Christian fellowship. In these things all is not vanity, though there will be some alloy as long as we are under the sun. Where two are closely joined in holy love and fellowship, Christ will by his Spirit come to them; then there is a threefold cord.