In this passage Paul addresses the tension between two groups within the Christian community ... Paul’s message urges the Roman Christians to withhold judgment of their fellow believers, which was a threat to unity.
Now -- Paul often moves from one subject to another by means of a transition; but he often simply turns from one subject to the next without a bridge of thought. That is the case here. Now (transitional δέ) - Lenski
Receive [accept; welcome] -- The present tense Greek word refers to personal and willing acceptance of another.
Same word and tense as Rom_15:7.
The exhortation here is directed to the strong, for they are tempted to enter into quarrels with those who have a weaker faith. - ESVSB
weak -- One not convinced of their liberty in Christ. - (NIVZSB)
one who is weak in the faith -- Likely refers to Christians who remained committed to observing certain parts of the law, such as food laws and the Sabbath (Rom_14:2-3).
The immediate context probably refers to Jewish Christians, though other practices concerning food and observing certain days (Rom_14:6) were issues for non-Jewish people as well (see Gal_4:1-11). The law of Moses designated certain animals as ritually unclean, and it therefore prohibited Jews from eating them (see Lev_11:1-47). - FSB
The strong Jewish believers understood their freedom in Christ and realized the ceremonial requirements of the Mosaic law were no longer binding. The mature Gentiles understood that idols are not gods and, therefore, that they could eat meat that had been offered to them. But in both cases the weaker brothers’ consciences were troubled, and they were even tempted to violate their consciences (a bad thing to train oneself to do), become more legalistic under the feelings of guilt, or even to sin. Knowing that the mature Jews and Gentiles would be able to understand these struggles, Paul addresses most of his comments to them. - MSB
Being weak in faith means having scruples against doing certain things that Christian liberty would allow. In Rome, most of the weak in faith were Jewish Christians whose consciences did not give them liberty from certain requirements of Jewish law. - NLTSB
weak in the faith -- This characterizes those believers who are unable to let go of the religious ceremonies and rituals of their past.
The weak Jewish believer had difficulty abandoning the rites and prohibitions of the Old Covenant; he felt compelled to adhere to dietary laws, observe the Sabbath, and offer sacrifices in the temple. The weak Gentile believer had been steeped in pagan idolatry and its rituals; he felt that any contact with anything remotely related to his past, including eating meat that had been offered to a pagan deity and then sold in the marketplace, tainted him with sin.
Both had very sensitive consciences in these areas, and were not yet mature enough to be free of those convictions. Cf. 1Co_8:1-13. - MSB
This [weak in faith] refers to a legalistic mindset. The over-scrupulous Christian brother is described in this chapter in three ways (1) prohibitions of food (cf. Rom_14:2, Rom_14:6, Rom_14:21); (2) emphasis on special days (cf. Rom_14:5-6); and (3) prohibition of wine (cf. Rom_14:17, Rom_14:21). This same type of person was mentioned in Rom_15:1 and 1Co_8:9-13; Rom_9:22. Be careful not to categorize yourself too quickly as a strong or weak Christian. Often believers are weak in one area and strong in another.
Paul’s attitude toward these matters is very different in Gal_4:9-10 and Col_2:16-23. These texts reflect the attitudes and teachings of false teachers. In Romans these are sincere believers who have over-scrupulous consciences. - Utley
the faith -- In his faith. Is the faith here to be understood at subjective, or objective as the gospel, the will of God in Christ. Probably subjective.
not to disputes [quarrel; judgment] --
Better translated, “for the purpose of passing judgment on his opinions (or scruples).” The mature believer should not sit in judgment on the sincere but underdeveloped thoughts that govern the weak believer’s conduct.
Lit. not to criticisms of (his) scruples. “receive him, do not criticize him; let him come with a welcome, —The noun rendered “criticisms” (or its cognate verb) is used (e.g. 1Co_12:10; Heb_5:14;) for detection of differences. (CBSC)
over doubtful things [over opinions;] --
In Rom 14 and 1Cor 8 Paul argues for mutual toleration. It is unmistakable, from all the passages in question, with which Paul sided. Paul clearly decides against the principle of the “weak brethren;” though he treats it as an error which might lawfully and usefully be met by toleration. (CBSC)
The last word in the verse is διαλογισμός (dialogismos), which basically means “a thought, an opinion,” and can mean “a doubt, a dispute.” The best translation in this context is simply “opinions,” which is after all the subject of the whole section. The NASB says it best: “but not for the purpose of passing judgment on his opinions.” - CPNIV
Hope this is helpful.
J.
P.S.
@Ernest T. Bass handle on righteousness is correct, see for yourself how many garments are there for the believer to put on in the Imperative Tense.