Hastings' Dictionary of the New Testament 
It is obvious that the transition from Judaism to Christianity could hardly be made without difficulty. To the Jew it must have seemed almost incredible that he should divest himself of the observance of Mosaic Law, and equally incredible that the Gentile should be admitted into the Kingdom of God without accepting the same Law. It was inevitable that the question should soon arise in the early days of the Church, whether the Church of the future should be Catholic or Jewish. It was only to be expected that this controversy should give rise to a party in the Church who were in favour of the latter alternative, consisting of those who, being Christians, yet retained their affection for the Mosaic Law and wished to impose it upon every member of the Christian Church. On the other hand, the keen intellect of a Stephen or a Paul saw at once that any attempt to enforce the Mosaic Law or even the initiatory rite of circumcision upon the Gentiles, meant stagnation and death to the Church.
No inconsiderable part of the Acts and the Epistles is taken up with the description of the attempts of the Judaizers to gain their end, and of the resolute resistance to them of St. Paul and those who thought with him.
1. In the Acts. -In the Acts the three most important crises of this question are ( a ) the speech of St. Stephen, ( b ) the conversion of Cornelius, and ( c ) the Council at Jerusalem.
( a ) The importance of St. Stephen’s speech consists in the principles which underlie the historical summary which is its main feature. He had been accused of blaspheming the Temple and the Law. No doubt, the charges were exaggerated and his language distorted by false witnesses. But there was that half truth in them which made them colourable. The principles which come out in the speech are those which we can also trace in Christ’s attitude towards Judaism, viz. that Christianity would fulfil and also succeed the older dispensation.
( b ) The importance of the incident of Cornelius is emphasized by the two-fold account of it in the Acts and by the two special manifestations of the Divine will made to St. Peter to teach him what he should do. The vision of the sheet, with the clean and unclean animals, showed that the Apostle’s act was a new departure, requiring special and Divine sanction; and the outpouring of the Holy Spirit, prior to baptism, was needed to teach him that he might initiate his converts into the Christian Church by that sacrament.
( c ) Now, as the first of these incidents had dealt with the general principles regulating the relation of Christianity to Judaism, and the second had shown that Gentiles were to be admitted into the Christian body, so the third determined what requirements, if any, should be made of Gentile converts. The four precepts required are not to be regarded simply as concessions to Jewish prejudices. Three out of the four deal with great mysteries of human life and induce corresponding forms of reverence. Nor were these precepts intended to be applied either universally or permanently, but rather to meet a local and temporary difficulty.
In addition to these three important incidents, there are many references in the Acts to this question, showing the prominent place it took in the Church thought and life of the day. We cannot go into all these references, but, as an example, we may quote the narrative in Acts 21:20 ff. in which St. Paul is advised to take some step that may disarm the prejudices of the Judaizers against him.
2. In St. Paul’s Epistles. -When we turn to the Epistles, we have to notice that St. Paul was attacked on personal as well as on doctrinal grounds, and that his authority as an apostle was called in question. This was especially the case at Corinth, as we learn from the Second Epistle to the Corinthians. In the First Epistle he had dealt with the divisions in that Church (see Divisions). But in the Second Epistle he defends his own apostolic authority. He could produce no commendatory letter from the Church in Jerusalem as his opponents were able to do, nor would he do so; he did not derive his authority from any apostle, but direct from the Lord Jesus Himself.
When we turn to the Epistle to the Galatians, we find the controversy accentuated. The Galatians had been ‘bewitched’ by the Jewish emissaries. They had relapsed from the simplicity of the gospel into the ceremonialism of Judaism. The authority of the Apostle had been disparaged and denied. St. Paul was evidently deeply stirred, as well as fully conscious of the danger to Christianity which was caused by the action of the Judaizers. The result was an Epistle which, in burning words, pleads for the liberty of the gospel and warns against the retrograde step of again submitting to the bondage of the Law.
The Church in Coloassae was affected by the Judaism of the Dispersion, which differed in some respects from the Judaism of Jerusalem. The view of the Colossian heresy which was held formerly, as expounded by J. B. Lightfoot in his Commentary (31879, p. 74f.), was that this heresy was a form of Gnosticism, but F. J. A. Hort in his Judaistic Christianity (1894, p. 116ff.) contends that St. Paul had in mind a form of Judaism rather than of Gnosticism. It is not the Judaism of Jerusalem which laid stress upon the importance of circumcision and the Law, but the Judaism of the Dispersion, which concerned itself with such questions as difference of food, difference or days, etc. ( Colossians 2:16; Colossians 2:20-21). According to this view, the φιλοσοφία of Colossians 2:8 refers to the detailed passage in Colossians 2:16-23, and the meats, drinks, feasts, new moons, and Sabbaths, are Judaic.
Hort also takes the same view with regard to the Pastoral Epistles, and concludes his argument as follows:
‘On the whole then in the Pastoral Epistles, no less than in Colossians, it seems impossible to find clear evidence of speculative or Gnosticising tendencies. We do find however a dangerous fondness for Jewish trifling, both of the legendary and of the legal or casuistical kind. We find also indications, but much less prominent, of some such abstinences in the matter of foods (probably chiefly animal food and wine) as at Colossae and Rome, with a probability that marriage would before long come likewise under a religious ban. But of circumcision and the perpetual validity of the Law we have nothing’ (p. 146).
3. In the Epistle to the Hebrews. -With all the mystery which surrounds the identity of the author of the Epistle to the Hebrews and the community to which it was addressed, it is clear that the whole argument is directed against the Judaizers. The people addressed are evidently in danger of apostasy. They do not see what the gospel can offer them in exchange for the loss they have sustained in being expelled from the synagogue.
It is not necessary here to detail the argument of the Epistle, which may be studied in the articleon Hebrews, Ep. to the, or in the article in Hasting's Dictionary of the Bible (5 vols) ; but the superiority of Christ over Judaism is its main burden, and the Epistle is pregnant with the difficulties of Christianity confronted with Judaizing teachers. It deals with those who, as Hort says, ‘without abjuring the name of Jesus, … treat their relation to him as trivial and secondary compared with their relation to the customs of their forefathers and their living countrymen’ (p. 157).
In conclusion, we may say that Judaistic Christianity was a natural product of the circumstances of the Apostolic Age, a product which was destined to be a source of internal trouble to the primitive Church. It lived on for some time, with occasional outbursts of revival, and at length died naturally away.
Judaism decreased as Christianity increased. Jews who became Christians were not forbidden to observe the laws and customs to which they were attached, but were enjoined to seek beneath the letter of the ordinance for the truth of which it was the exponent. No attempt was to be made to enforce upon Gentile Christians the bondage of the Law or to take away the liberty with which Christ had made them free.
Literature.-In addition to the works already mentioned, see. R. J. Knowling. ‘Acts,’ in Expositor’s Greek Testament , 1900; W. M. Ramsay, St. Paul the Traveller and the Roman Citizen , 1895; F. W. Farrar, Life and Work of St. Paul , 1897; K. Lake, The Earlier Epistles of St. Paul , 1911, p. 14; A. de Boysson, La Loi et la Foi , 1912.
Webster's Dictionary 
(p. pr. & vb. n.) of Judaize