Romans 14:5-6

5One person esteems one day above another; another esteems every day alike. Let each be fully convinced in his own mind.

6He who observes the day, observes it to the Lord; and he who does not observe the day, to the Lord he does not observe it. He who eats, eats to the Lord, for he gives God thanks; and he who does not eat, to the Lord he does not eat, and gives God thanks.