John Wesley on Revelation 14:1

And I saw on mount Sion - The heavenly Sion. An hundred forty - four thousand - Either those out of all mankind who had been the most eminently holy, or the most holy out of the twelve tribes of Israel the same that were mentioned, Rev 7:4, and perhaps also, Rev 16:2. But they were then in the world, and were sealed in their foreheads, to preserve them from the plagues that were to follow. They are now in safety, and have the name of the Lamb and of his Father written on their foreheads, as being the redeemed of God and of the Lamb, his now unalienable property. This prophecy often introduces the inhabitants of heaven as a kind of chorus with great propriety and elegance. The church above, making suitable reflections on the grand events which are foretold in this book, greatly serves to raise the attention of real Christians, and to teach the high concern they have in them. Thus is the church on earth instructed, animated, and encouraged, by the sentiments temper, and devotion of the church in heaven.