A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
num 15:1THE LAW OF SUNDRY OFFERINGS. (Num. 15:1-41)
The Lord spake unto Moses, saying, Speak unto the children of Israel--Some infer from Num 15:23 that the date of this communication must be fixed towards the close of the wanderings in the wilderness; and, also, that all the sacrifices prescribed in the law were to be offered only after the settlement in Canaan.
num 15:3make an offering by fire unto the Lord, a burnt offering--It is evident that a peace offering is referred to because this term is frequently used in such a sense (Exo 18:12; Lev 17:5).
num 15:4tenth deal--that is, an omer, the tenth part of an ephah (Exo 16:36).
fourth part of an hin of oil--This element shows it to have been different from such meat offerings as were made by themselves, and not merely accompaniments of other sacrifices.
num 15:6two tenth deals--The quantity of flour was increased because the sacrifice was of superior value to the former. The accessory sacrifices were always increased in proportion to the greater worth and magnitude of its principal.
num 15:13a stranger--one who had become a proselyte. There were scarcely any of the national privileges of the Israelites, in which the Gentile stranger might not, on conforming to certain conditions, fully participate.
num 15:19when ye eat of the bread of the land, ye shall offer up an heave offering--The offering prescribed was to precede the act of eating.
unto the Lord--that is, the priests of the Lord (Eze 44:30).
num 15:20heave offering of the threshing-floor--meaning the corn on the threshing-floor; that is, after harvest.
so shall ye heave it--to the priests accompanying the ceremony with the same rites.
num 15:22if ye have erred, and not observed all these commandments, &c.--respecting the performance of divine worship, and the rites and ceremonies that constitute the holy service. The law relates only to any omission and consequently is quite different from that laid down in Lev 4:13, which implies a transgression or positive neglect of some observances required. This law relates to private parties or individual tribes; that to the whole congregation of Israel.
num 15:24if aught be committed by ignorance--The Mosaic ritual was complicated, and the ceremonies to be gone through in the various instances of purification which are specified, would expose a worshipper, through ignorance, to the risk of omitting or neglecting some of them. This law includes the stranger in the number of those for whom the sacrifice was offered for the sin of general ignorance.
num 15:27if any soul sin through ignorance--not only in common with the general body of the people, but his personal sins were to be expiated in the same manner.
num 15:30the soul that doeth aught presumptuously--Hebrew, "with an high" or "uplifted hand"--that is, knowingly, wilfully, obstinately. In this sense the phraseology occurs (Exo 14:8; Lev 26:21; Psa 19:13).
the same reproacheth the Lord--sets Him at open defiance and dishonors His majesty.
num 15:31his iniquity shall be upon him--The punishment of his sins shall fall on himself individually; no guilt shall be incurred by the nation, unless there be a criminal carelessness in overlooking the offense.
num 15:32a man that gathered sticks upon the sabbath day--This incident is evidently narrated as an instance of presumptuous sin. The mere gathering of sticks was not a sinful act and might be necessary for fuel to warm him or to make ready his food. But its being done on the Sabbath altered the entire character of the action. The law of the Sabbath being a plain and positive commandment, this transgression of it was a known and wilful sin, and it was marked by several aggravations. For the deed was done with unblushing boldness in broad daylight, in open defiance of the divine authority--in flagrant inconsistency with His religious connection with Israel, as the covenant-people of God; and it was an application to improper purposes of time, which God had consecrated to Himself and the solemn duties of religion. The offender was brought before the rulers, who, on hearing the painful report, were at a loss to determine what ought to be done. That they should have felt any embarrassment in such a case may seem surprising, in the face of the sabbath law (Exo 31:14). Their difficulty probably arose from this being the first public offense of the kind which had occurred; and the appeal might be made to remove all ground of complaint--to produce a more striking effect, so that the fate of this criminal might be a beacon to warn all Israelites in the future.
num 15:35The Lord said unto Moses, The man shall be surely put to death--The Lord was King, as well as God of Israel, and the offense being a violation of the law of the realm, the Sovereign Judge gave orders that this man should be put to death; and, moreover, He required the whole congregation unite in executing the fatal sentence.
num 15:38bid them that they make them fringes in the borders of their garments--These were narrow strips, in a wing-like form, wrapped over the shoulders and on various parts of the attire. "Fringe," however, is the English rendering of two distinct Hebrew words--the one meaning a narrow lappet or edging, called the "hem" or "border" (Mat 23:5; Luk 8:44), which, in order to make it more attractive to the eye and consequently more serviceable to the purpose described, was covered with a riband of blue or rather purple color; the other term signifies strings with tassels at the end, fastened to the corners of the garment. Both of these are seen on the Egyptian and Assyrian frocks; and as the Jewish people were commanded by express and repeated ordinances to have them, the fashion was rendered subservient, in their case, to awaken high and religious associations--to keep them in habitual remembrance of the divine commandments.
num 15:41I am the Lord your God--The import of this solemn conclusion is, that though He was displeased with them for their frequent rebellions, for which they would be doomed to forty years' wanderings, He would not abandon them but continue His divine protection and care of them till they were brought into the land of promise.