Philippians 1:3 - Albert Barnes' Notes on the Bible

I thank my God upon every remembrance of you - Margin, “mention.” The Greek word means, “recollection, remembrance.” But this recollection may have been suggested either by his own reflections on what he had seen, or by what he had heard of them by others, or by the favors which they conferred on him reminding him of them. The meaning is, that as often as he thought on them, from whatever cause, he had occasion of thankfulness. He says that he thanked his God, intimating that the conduct of the Philippians was a proof of the favor of God to him; that is, he regarded their piety as one of the tokens of the favor of God to his own soul - for in producing that piety he had been mainly instrumental.