For concerning the ministering to the saints, it is unnecessary for me to write to you:
All Commentaries on 2 Corinthians 9:1 Go To 2 Corinthians 9
Ambrosiaster
AD 400
It is superfluous, but in order to demonstrate his diligence, it was necessary for Paul to write like this, so that they would be all the more willing to do what they were asked and to embody the truth they were being taught. For superfluities tend to show greater concern. Our Lord did not doubt Peter’s love for him, but even so he asked the apostle three times: “Simon, son of John, do you love me?” This repetition may seem to be superfluous, but it contributed to the perfecting of the admonition. At length Peter would learn from it that he must act with great diligence. Commentary on Paul’s Epistles.