Romans 14:5,6 (KJV)
5 One man esteemeth one day above another: another esteemeth every day alike . Let every man be fully persuaded in his own mind.
6 He that regardeth the day, regardeth it unto the Lord; and he that regardeth not the day, to the Lord he doth not regard it . He that eateth, eateth to the Lord, for he giveth God thanks; and he that eateth not, to the Lord he eateth not, and giveth God thanks.