He that regards the day, regards it unto the Lord; and he that regards not the day, to the Lord he does not regard it. He that eats, eats to the Lord, for he gives God thanks; and he that eats not, to the Lord he eats not, and gives God thanks.
Read Chapter 14
Augustine of Hippo
AD 430
When someone observes the day well, he keeps the day for the Lord. To judge the day well means you are not to despair over the future correction of the person whose guilt might appear now to be clean. .
And a little way on he explains the reason of the command, when he says, "He that eateth, eateth to the Lord, and giveth God thanks; and he that eateth not, to the Lord he eateth not, and giveth God thanks."
Paul continues his exposition [from the previous verse]. The issue at stake is not a fundamental one. Both sides are acting for God’s sake, and both end up by giving him thanks. Thus the difference between them turns out to be a minor one. Nevertheless, Paul aims a blow at the Judaizers, because he accepts the validity of all foods.