Paul followed Christ and Christ therefore obviously said 'one person regards one day above another, another regards every day alike. Each person must be fully convinced in his own mind.'
Given what is written about man, why should I build my doctrine around what one guys says, or another guys says who are weak in the Faith? We either believe the God of the Bible and His Word's or we don't. Don't we all have to be convinced in our own mind?
Was Abraham weak in Faith? Of course not.
Gen. 26:
4 And I will make thy seed to multiply as the stars of heaven, and will give unto thy seed all these countries; and in thy seed shall all the nations of the earth be blessed;
5 Because that Abraham obeyed my voice, and kept my charge, my commandments, my statutes, and my laws.
Rom. 4:
16 Therefore it is of faith, that it might be by grace; to the end the promise might be sure to all the seed; not to that only which is of the law,(Those cleansed by the Levitical Priesthood Abraham didn't have) but to that also which is of the
faith of Abraham; who is the father of us all,
Paul Followed Christ, Christ followed God. There is one God, one faith, Abraham had that faith as it is written. Let each man be fully convinced in his own mind.