2 Peter 1:8
For if these things are yours and abound, they make you to be not idle nor unfruitful to the knowledge of our Lord Jesus Christ.
2 Timothy 2:21
If anyone therefore purges himself from these, he will be a vessel for honor, sanctified, and suitable for the master's use, prepared for every good work.
"Can a man be profitable to God? Surely he who is wise is profitable to himself.
I beg you for my child, whom I have become the father of in my chains, Onesimus,
who once was useless to you, but now is useful to you and to me.
2 Timothy 4:11
Only Luke is with me. Take Mark, and bring him with you, for he is useful to me for service.