Daily Devotional, Monday, August 20, 2012, "God's Stamp of Approval" -

“For we dare not class ourselves or compare ourselves with those who commend themselves. But they, measuring themselves by themselves, and comparing themselves among themselves, are not wise. We, however, will not boast beyond measure, but within the limits of the sphere which God appointed us--a sphere which especially includes you. For we are not overextending ourselves (as though [our authority] did not extend to you), for it was to you that we came with the gospel of Christ; not boasting of things beyond measure, [that is], in other men's labors, but having hope, [that] as your faith is increased, we shall be greatly enlarged by you in our sphere, to preach the gospel in the [regions] beyond you, [and] not to boast in another man's sphere of accomplishment. But "he who glories, let him glory in the LORD." For not he who commends himself is approved, but whom the Lord commends.” I Corinthians 10:12-19