John Lightfoot on Matthew 10:5

[Into any city of the Samaritans, enter ye not.] Our Saviour would have the Jews' privileges reserved to them, until they alienated and lost them by their own perverseness and sins. Nor does he grant the preaching of the gospel to the Gentiles or Samaritans, before it was offered to the Jewish nation. The Samaritans vaunted themselves sons of the patriarch Jacob, John 4:12 (which, indeed, was not altogether distant from the truth); they embraced also the law of Moses; and being taught thence, expected the Messias as well as the Jews: nevertheless, Christ acknowledges them for his sheep no more than the heathen themselves.

I. Very many among them were sprung, indeed, of the seed of Jacob, though now become renegades and apostates from the Jewish faith and nation, and hating them more than if they were heathens, and more than they would do heathens. Which also, among other things, may perhaps be observed in their very language. For read the Samaritan version of the Pentateuch; and, if I mistake not, you will observe that the Samaritans, when, by reason of the nearness of the places, and the alliance of the nations, they could not but make use of the language of the Jews, yet used such a variation and change of the dialect, as if they scorned to speak the same words that they did, and make the same language not the same.

II. In like manner they received the Mosaic law, but, for the most part, in so different a writing of the words, that they seem plainly to have propounded this to themselves, that retaining indeed the law of Moses, they would hold it under as much difference from the Mosaic text of the Jews as ever they could, so that they kept something to the sense. "R. Eliezer Ben R. Simeon said, 'I said to the scribes of the Samaritans, Ye have falsified your law without any manner of profit accruing to you thereby. For ye have written in your law, near the oaken groves of Moreh, which is Sychem,'" &c....Let the Samaritan text at Deuteronomy 11:30 be looked upon.

III. However they pretended to study the religion of Moses, yet, in truth, there was little or no difference between them and idolaters, when they knew not what they worshipped; which our Saviour objects against them, John 4:22: and had not only revolved as apostates from the true religion of Moses, but set themselves against it with the greatest hatred. Hence the Jewish nation held them for heathens, or for a people more execrable than the heathens themselves. A certain Rabbin thus reproaches their idolatry: "R. Ismael Ben R. Josi went to Neapolis [that is, Sychem]: the Samaritans came to him, to whom he spake thus; 'I see that you adore not this mountain, but the idols which are under it: for it is written, Jacob hid the strange gods under the wood, which is near Sychem.'"

It is disputed whether a Cuthite ought to be reckoned for a heathen, which is asserted by Rabbi, denied by Simeon; but the conclusion, indeed, is sufficiently for the affirmative.

IV. The metropolis of the Samaritans laboured under a second apostasy, being brought to it by the deceit and witchcraft of Simon Magus, after the receiving of the gospel from the mouth of our Saviour himself. Compare Acts 8:9 with John 4:41.

From all these particulars, and with good reason for the thing itself, and to preserve the privileges of the Jews safe, and that they might not otherwise prove an offence to that nation, the Samaritans are made parallel to the heathen, and as distant as they from partaking of the gospel.