Jamieson, Fausset and Brown on Romans 14:14-15

14-15. I know, and am persuaded by--or rather, "in"

the Lord Jesus--as "having the mind of Christ" (1Co 2:16).

that there is nothing unclean of itself--Hence it is that he calls those "the strong" who believed in the abolition of all ritual distinctions under the Gospel. (See Ac 10:15).

but--"save that"

to him that esteemeth anything to be unclean, to him it is unclean--"and therefore, though you can eat of it with out sin, he cannot."