The one who observes the day observes it for the Lord. And the one who eats, eats for the Lord, because he gives thanks (eucharistei | εὐχαριστεῖ | pres act ind 3 sg) to God; and the one who abstains from eating, abstains for the Lord and gives (eucharistei | εὐχαριστεῖ | pres act ind 3 sg) thanks to God.
Reference
Romans 14:6
Sequence
16