(KJV)1 Corinthians 7:5-6
Defraud ye not one the other, except it be with consent for a time, that ye may give yourselves to fasting and prayer; and come together again, that Satan tempt you not for your incontinency.  But I speak this by permission, and not of commandment.
(KJV)1 Corinthians 7:12
But to the rest speak I, not the Lord: If any brother hath a wife that believeth not, and she be pleased to dwell with him, let him not put her away.
Paul gives these concessions/permissions in reply to a letter the Corinthians had written him, Since these concessions/permissions which were not commandments concerned the church at corinth,should they be binding to other churches?