One person considers one day more sacred than another; another considers every day alike. Each of them should be fully convinced in their own mind. Whoever regards one day as special does so to the Lord. Whoever eats meat does so to the Lord, for they give thanks to God; and whoever abstains does so to the Lord and gives thanks to God. For none of us lives for ourselves alone, and none of us dies for ourselves alone. If we live, we live for the Lord; and if we die, we die for the Lord. So, whether we live or die, we belong to the Lord. For this very reason, Christ died and returned to life so that he might be the Lord of both the dead and the living.
Romans 14:5-9 (NIV)