And when David was come to the camp, Sobi the son of Naas of Rabbath of the children of Ammon, and Machir the son of Ammihel of Lodabar, and Berzellai the Galaadite of Rogelim,

And as soon as David came to Mahanaim, Shobi the son of Nahash of Rabbah of the children of Ammon, and Machir the son of Ammiel of Lo-debar, and Barzillai the Gileadite of Rogelim,

And it came to pass, when David was come to Mahanaim, that Shobi the son of Nahash of Rabbah of the children of Ammon, and Machir the son of Ammiel of Lo-debar, and Barzillai the Gileadite of Rogelim,

And it cometh to pass at the coming in of David to Mahanaim, that Shobi, son of Nahash, from Rabbah of the Bene-Ammon, and Machir son of Ammiel, from Lo-Debar, and Barzillai the Gileadite, from Rogelim,

Now when David had come to Mahanaim, Shobi, the son of Nahash of Rabbah, the Ammonite, and Machir, the son of Ammiel of Lo-debar, and Barzillai the Gileadite of Rogelim,

And when David had arrived at the encampment, Shobi, the son of Nahash, from Rabbah, of the sons of Ammon, and Machir, the son of Ammiel of Lodebar, and Barzillai, the Gileadite of Rogelim,

Shobi's father may have been the king of the Ammonites, and Shobi appointed by David as tributary king or governor of Ammon after he took Rabbah 2-Samuel 12:29. On the other hand, Nahash may have been a common name among the Ammonites, and the Nahash of 2-Samuel 17:25 may have been of that nation.
On Machir, see the marginal reference.
Barzillai was ancestor, through a daughter, to a family of priests, who were called after him "sons of Barzillai," and who returned from captivity with Zerubbabel, but were not allowed to officiate as priests, or eat of the holy things, through defect of a proper register Ezra 2:61-63. It is likely that being wealthy they had neglected their priestly privileges, as a means of maintenance, before the captivity.
Rogelim was situated in the highlands of Gilead, but the exact situation is not known. It means "the fullers," being the plural of the word "Rogel," in "En-Rogel," 2-Samuel 17:17.

And it came to pass, when David was come to Mahanaim,.... When he first came thither, 2-Samuel 17:24,
that Shobi the son of Nahash of Rabbah of the children of Ammon: who was either the son, or rather the brother of Hanun king of the Ammonites, that used David's ambassadors in so shameful a manner, whom David overcame and deposed, and set up this brother in his room; who had showed his dislike of his brother's conduct, and now makes a grateful return to David for his favours; though some say this was Hanun himself, as Jarchi, now become a proselyte, which is not so likely; others take this man to be an Israelite that continued in Rabbah, the metropolis of the Ammonites, after it was taken by David:
and Machir the son of Ammiel of Lodebar; the same that brought up Mephibosheth, from whom David received him and took him off of his hands, for which now he requited him, see 2-Samuel 9:5,
and Barzillai the Gileadite of Rogelim; a place that lay under the hills of Gilead (y); it had its name from the "fullers" who dwelt here for the convenience of fountains of water to wash their clothes in.
(y) Fuller's Pisgah-View, B. 2. c. 3. sect. 10. p. 94.

when David was come to Mahanaim--The necessities of the king and his followers were hospitably ministered to by three chiefs, whose generous loyalty is recorded with honor in the sacred narrative.
Shobi--must have been a brother of Hanun. Disapproving, probably, of that young king's outrage upon the Israelite ambassadors, he had been made governor of Ammon by David on the conquest of that country.
Machir--(See 2-Samuel 9:4). Supposed by some to have been a brother of Bath-sheba, and
Barzillai--a wealthy old grandee, whose great age and infirmities made his loyal devotion to the distressed monarch peculiarly affecting. The supplies they brought, which (besides beds for the weary) consisted of the staple produce of their rich lands and pastures, may be classified as follows: eatables--wheat, barley, flour, beans, lentils, sheep, and cheese; drinkables--"honey and butter" or cream, which, being mixed together, form a thin, diluted beverage, light, cool, and refreshing. Being considered a luxurious refreshment (Song 4:11), the supply of it shows the high respect that was paid to David by his loyal and faithful subjects at Mahanaim.

When David came to Mahanaim, some of the wealthier citizens of the land to the east of the Jordan supplied the men who were with him with provisions. This is mentioned as the first sign that the people had not all fallen away from David, but that some of the more distinguished men were still firm in their adherence. Shobi, the son of Nahash or Rabbah, the capital of the Ammonites (see 2-Samuel 11:1), was possibly a son of Nahash the deceased king of the Ammonites, and brother of Hanun, who was defeated by David (2-Samuel 10:1-2), and one of those to whom David had shown favour and kindness when Rabbah was taken. At the same time, it is also quite possible that Shobi may have been an Israelite, who was merely living in the capital of the Ammonites, which had been incorporated into the kingdom of David, as it is evident from 2-Samuel 17:25 that Nahash was not an uncommon name among the Israelites. Machir the son of Ammiel of Lodebar (see at 2-Samuel 9:4), and Barsillai of Roglim the Gileadite. Roglim was a town in Gilead, which is only mentioned once again, viz., in 2-Samuel 19:32, and of which nothing further is known. They brought "bedding, basins, earthenware, and wheat, barley, meal, and parched grains, beans, lentils and parched." The position of the verb, which is not placed between the subject and the object of the sentence, but only at the close of the whole series of objects, is certainly unusual; but this does not warrant any alteration of the text. For if we were to supply a verb before משׁכּב, as having fallen out of the text, it would be necessary, since הגּישׁוּ follows without a copula, to divide the things enumerated into two classes, so as to connect one portion of the objects with הגּישׁוּ, which is obviously unnatural. The early translators who interpolate a verb before the objects have therefore also supplied the copula w before הגּישׁוּ. There is still less ground for supplying the number 10, as having dropped out before משׁכּב and ספּות, as the lxx have done, since none of the translators of the other ancient versions had any such reading. משׁכּב, couch or bed, is used here for bedding. ספּות, basins, probably field-kettles. The repetition of וקלי is very striking; nevertheless the second must not be struck out without further ground as a supposed copyist's error. As they not only ate parched ears or grains of wheat (see at Leviticus 2:14), but were also in the habit of drying pulse, pease, and lentils before eating them (vid., Harmar, Beobachtungen, i. pp. 255-6), the second קלי may be understood as referring to parched pulse. The ἁπ. λεγ. בּקר שׁפות signifies, according to the Chaldee and the Rabbins, cheese of oxen (i.e., of cows), and according to the conjecture of Roediger (Ges. Thes. p. 1462), a peculiar kind of cheese, such as the Aeneze in the province of Nedjid still make,
(Note: According to Burckhardt's account (Die Beduinen, p. 48), "after they have taken the butter from the butter-milk, they beat the latter again till it coagulates, and then dry it till it is quite hard. It is then rubbed to pieces, and in the spring every family stores up two or three lasts of it, which they eat mixed with butter.")
and for which the term σαφὼθ βοῶν retained by the lxx was probably the technical name. Theodotus, on the other hand, has γαλαθηνὰ μοσχάρια, milch-calves; and the Vulgate pingues vitulos, - both of them renderings which can certainly be sustained from the Arabic usage of speech, and would be more in accordance with the situation of the words, viz., after צאן. אמרוּ כּי, "for they said (or thought) the people have become hungry and faint and thirty in the desert," i.e., in their flight to Mahanaim.

Shobi - Who, as it may seem, disliked and disowned that barbarous action to the ambassadors; and therefore, when the rest were destroyed, was left king or governor of the residue of the Ammonites. Machir - See above 2-Samuel 9:4.