John Calvin Commentary 2 Corinthians 7:6

"Nevertheless he that comforteth the lowly, [even] God, comforted us by the coming of Titus;" — 2 Corinthians 7:6 (ASV)

Who comforteth the lowly. This is mentioned as a reason; for he means that consolation had been offered to him because he was weighed down by evils and almost overwhelmed, since God is accustomed to comfort the lowly, that is, those who are cast down.

Hence, a most profitable doctrine may be inferred: that the more we have been afflicted, the greater the consolation God has prepared for us. Hence, in the description here applied to God, there is an excellent promise contained, as if he had said that it is uniquely the role of God to comfort those who are miserable and are humbled to the dust.