2 Corinthians 10:15-16

15We do not go beyond our proper limit, boasting in the work of other men, but we have the hope that as your faith [in Christ and His divine power] continues to grow, our field among you may be greatly expanded [but still within the limits of our commission],

16so that we may preach the gospel even in the lands beyond you, but not to boast in work already accomplished in another one’s field of activity.