This service that you perform is not only supplying the needs1 of God's people but is also overflowing in many expressions of thanks to God.2
References for 2 Corinthians 9:12
Because of the service3 by which you have proved yourselves, men will praise God4 for the obedience that accompanies your confession5 of the gospel of Christ,6 and for your generosity7 in sharing with them and with everyone else.
References for 2 Corinthians 9:13
And in their prayers for you their hearts will go out to you, because of the surpassing grace God has given you.