A.T. Robertson Commentary Romans 14:23

"But he that doubteth is condemned if he eat, because [he eateth] not of faith; and whatsoever is not of faith is sin." — Romans 14:23 (ASV)

He that doubteth (ο διακρινομενος). Present middle participle of διακρινω, to judge between (δια), to hesitate. See Jas 1:6f. for this same picture of the double-minded man. Cf. Romans 4:20; Mr 11:23.

Is condemned (κατακεκριτα). Perfect passive indicative of κατακρινω (note κατα-), "stands condemned."

If he eat (εαν φαγη). Third class condition, εαν and second aorist active subjunctive. If in spite of his doubt, he eat.

Whatsoever is not of faith is sin (παν ο ουκ εκ πιστεως αμαρτια εστιν).

Faith (πιστις) here is subjective, one's strong conviction in the light of his relation to Christ and his enlightened conscience. To go against this combination is sin beyond a doubt. Some MSS. (A L etc.) put the doxology here which most place in 16:25-27. But they all give chapters 15 and 16. Some have supposed that the Epistle originally ended here, but that is pure speculation. Some even suggest two editions of the Epistle. But chapter 15 goes right on with the topic discussed in chapter 14.