Romans 14:5-6

One person regards one day as better [or more important] than another, while another regards every day [the same as any other]. Let everyone be fully convinced (assured, satisfied) in his own mind. He who observes the day, observes it for the Lord. He who eats, eats for the Lord, since he gives thanks to God; while he who abstains, abstains for the Lord and gives thanks to God.