Numbers 10:6

When ye blow an alarm the second time - A single alarm, as above stated, was a signal for the eastward division to march; two such alarms, the signal for the south division; and probably three for the west division, and four for the north. It is more likely that this was the case, than that a single alarm served for each, with a small interval between them. The camps, or grand divisions of this great army, always lay, as we have already seen, to the east, south, west, and north: and here the east and south camps alone are mentioned; the first containing Judah, Issachar, and Zebulun; the second, Reuben, Simeon, and Gad. The west and north divisions are not named, and yet we are sure they marched in consequence of express orders or signals, as well as the other two. There appears therefore a deficiency here in the Hebrew text, which is thus supplied by the Septuagint: Και σαλπιειτε σημασιαν τριτην, και εξαρουσιν αἱ παρεμβολαι αἱ παρεμβαλλουσαι παρα θαλασσαν· και σαλπιειτε σημασιαν τεταρτην, και εξαρουσιν αἱ παρεμβολαι αἱ παρεμβαλλουσαι προς βορῥαν. "And when ye blow a third alarm or signal, the camps on the west shall march: and when ye blow a fourth alarm or signal, the camps on the north shall march." This addition, however, is not acknowledged by the Samaritan, nor by any of the other versions but the Coptic. Nor are there any various readings in the collections of Kennicott and De Rossi, which countenance the addition in the above versions. Houbigant thinks this addition so evidently necessary, that he has inserted the Latin in his text, and in a note supplied the Hebrew words, and thinks that these words were originally in the Hebrew text, but happened to be omitted in consequence of so many similar words occurring so often in the same verse, which might dazzle and deceive the eye of a transcriber.

10:6 For their journeys - As a sign for them to march forward, and consequently for the rest to follow them.