What is the Biblical basis for requiring someone to have faithful children to become an elder?

Just had an enlightening chat with a preacher of a faith I'm not familiar with. When I congratulated him on his new pastorship, he corrected me saying that he wasn't a pastor, and among other things he believed he needed to have faithful children before he could become a pastor or elder. He indicated that there was scriptural basis for this, but I don't recall which scripture he used, other than the New Testament in the KJV bible. **What scriptures support the idea that faithful children are needed prior to attaining a certain office or title?**