And when you blow an alarm the second time, the camps that are on the south side shall set out. An alarm is to be blown whenever they are to set out.
We have here directions concerning the public notices that were to be given to the people upon several occasions by sound of trumpet. In a thing of this nature, one would think, Moses needed not to have been taught of God: his own reason might teach him the conveniency of trumpets; but the constitution of Israel was to be in every thing divine, and therefore...
Commenting on Numbers 10:1-10
When ye blow an alarm the second time,.... Another "tara-tan-tara": then the camps that lie on the south side shall take their journey; the camps of Reuben, Simeon, and Gad, which were encamped on the south side of the tabernacle, Num 2:10; and, as Josephus (k) says, at the third sounding of the alarm, that part of the camp which lay to the west moved...
When ye blow an alarm the second time, then the camps that lie on the south side shall take their journey: they shall blow an alarm for their journeys. (c) Meaning, the heart of Reuben.