And Moses sent them to the war, a thousand of every tribe, them and Phinehas the son of Eleazar the priest, to the war, with the holy instruments, and the trumpets to blow in his hand. (Numbers 31:6)
That is, commissioned them with authority to carry out God’s command.
Phinehas.
We are not told whether Phinehas went as commander of the expedition, thereby superseding Joshua, or whether he went solely in his role as chief priest (see Joshua 22:13). His former deed of valor for the honor of God had no doubt given him a great reputation for decision and courage (ch. 25:8).
The holy instruments.
That is, the sacred vessels. We are not told which vessels were taken. Some have suggested the ark (see Num. 10:33; Joshua 3:14; 6:8), others, the plate of gold that Aaron wore upon his head (Ex. 28:36). The word here translated “instruments” is the same as that rendered “vessels” in Num. 3:31. It may be permissible to think of the trumpets of the sanctuary as being “holy instruments.”