Albert Barnes Commentary Numbers 7:12-83

"And he that offered his oblation the first day was Nahshon the son of Amminadab, of the tribe of Judah: and his oblation was one silver platter, the weight whereof was a hundred and thirty [shekels], one silver bowl of seventy shekels, after the shekel of the sanctuary; both of them full of fine flour mingled with oil for a meal-offering; one golden spoon of ten [shekels], full of incense; one young bullock, one ram, one he-lamb a year old, for a burnt-offering; one male of the goats for a sin-offering; and for the sacrifice of peace-offerings, two oxen, five rams, five he-goats, five he-lambs a year old: this was the oblation of Nahshon the son of Amminadab. On the second day Nethanel the son of Zuar, prince of Issachar, did offer: he offered for his oblation one silver platter, the weight whereof was a hundred and thirty [shekels], one silver bowl of seventy shekels, after the shekel of the sanctuary; both of them full of fine flour mingled with oil for a meal-offering; one golden spoon of ten [shekels], full of incense; one young bullock, one ram, one he-lamb a year old, for a burnt-offering; one male of the goats for a sin-offering; and for the sacrifice of peace-offerings, two oxen, five rams, five he-goats, five he-lambs a year old: this was the oblation of Nethanel the son of Zuar. On the third day Eliab the son of Helon, prince of the children of Zebulun.: his oblation was one silver platter, the weight whereof was a hundred and thirty [shekels], one silver bowl of seventy shekels, after the shekel of the sanctuary; both of them full of fine flour mingled with oil for a meal-offering; one golden spoon of ten [shekels], full of incense; one young bullock, one ram, one he-lamb a year old, for a burnt-offering; one male of the goats for a sin-offering; and for the sacrifice of peace-offerings, two oxen, five rams, five he-goats, five he-lambs a year old: this was the oblation of Eliab the son of Helon. On the fourth day Elizur the son of Shedeur, prince of the children of Reuben: his oblation was one silver platter, the weight whereof was a hundred and thirty [shekels], one silver bowl of seventy shekels, after the shekel of the sanctuary; both of them full of fine flour mingled with oil for a meal-offering; one golden spoon of ten [shekels], full of incense; one young bullock, one ram, one he-lamb a year old, for a burnt-offering; one male of the goats for a sin-offering; and for the sacrifice of peace-offerings, two oxen, five rams, five he-goats, five he-lambs a year old: this was the oblation of Elizur the son of Shedeur. On the fifth day Shelumiel the son of Zurishaddai, prince of the children of Simeon: his oblation was one silver platter, the weight whereof was a hundred and thirty [shekels], one silver bowl of seventy shekels, after the shekel of the sanctuary; both of them full of fine flour mingled with oil for a meal-offering; one golden spoon of ten [shekels], full of incense; one young bullock, one ram, one he-lamb a year old, for a burnt-offering; one male of the goats for a sin-offering; and for the sacrifice of peace-offerings, two oxen, five rams, five he-goats, five he-lambs a year old: this was the oblation of Shelumiel the son of Zurishaddai. On the sixth day Eliasaph the son of Deuel, prince of the children of Gad: his oblation was one silver platter, the weight whereof was a hundred and thirty [shekels], one silver bowl of seventy shekels, after the shekel of the sanctuary; both of them full of fine flour mingled with oil for a meal-offering; one golden spoon of ten [shekels], full of incense; one young bullock, one ram, one he-lamb a year old, for a burnt-offering; one male of the goats for a sin-offering; and for the sacrifice of peace-offerings, two oxen, five rams, five he-goats, five he-lambs a year old: this was the oblation of Eliasaph the son of Deuel. On the seventh day Elishama the son of Ammihud, prince of the children of Ephraim: his oblation was one silver platter, the weight whereof was a hundred and thirty [shekels], one silver bowl of seventy shekels, after the shekel of the sanctuary; both of them full of fine flour mingled with oil for a meal-offering; one golden spoon of ten [shekels], full of incense; one young bullock, one ram, one he-lamb a year old, for a burnt-offering; one male of the goats for a sin-offering; and for the sacrifice of peace-offerings, two oxen, five rams, five he-goats, five he-lambs a year old: this was the oblation of Elishama the son of Ammihud. On the eighth day Gamaliel the son of Pedahzur, prince of the children of Manasseh: his oblation was one silver platter, the weight whereof was a hundred and thirty [shekels], one silver bowl of seventy shekels, after the shekel of the sanctuary; both of them full of fine flour mingled with oil for a meal-offering; one golden spoon of ten [shekels], full of incense; one young bullock, one ram, one he-lamb a year old, for a burnt-offering; one male of the goats for a sin-offering; and for the sacrifice of peace-offerings, two oxen, five rams, five he-goats, five he-lambs a year old: this was the oblation of Gamaliel the son of Pedahzur. On the ninth day Abidan the son of Gideoni, prince of the children of Benjamin: his oblation was one silver platter, the weight whereof was a hundred and thirty [shekels], one silver bowl of seventy shekels, after the shekel of the sanctuary; both of them full of fine flour mingled with oil for a meal-offering; one golden spoon of ten [shekels], full of incense; one young bullock, one ram, one he-lamb a year old, for a burnt-offering; one male of the goats for a sin-offering; and for the sacrifice of peace-offerings, two oxen, five rams, five he-goats, five he-lambs a year old: this was the oblation of Abidan the son of Gideoni. On the tenth day Ahiezer the son of Ammishaddai, prince of the children of Dan: his oblation was one silver platter, the weight whereof was a hundred and thirty [shekels], one silver bowl of seventy shekels, after the shekel of the sanctuary; both of them full of fine flour mingled with oil for a meal-offering; one golden spoon of ten [shekels], full of incense; one young bullock, one ram, one he-lamb a year old, for a burnt-offering; one male of the goats for a sin-offering; and for the sacrifice of peace-offerings, two oxen, five rams, five he-goats, five he-lambs a year old: this was the oblation of Ahiezer the son of Ammishaddai. On the eleventh day Pagiel the son of Ochran, prince of the children of Asher: his oblation was one silver platter, the weight whereof was a hundred and thirty [shekels], one silver bowl of seventy shekels, after the shekel of the sanctuary; both of them full of fine flour mingled with oil for a meal-offering; one golden spoon of ten [shekels], full of incense; one young bullock, one ram, one he-lamb a year old, for a burnt-offering; one male of the goats for a sin-offering; and for the sacrifice of peace-offerings, two oxen, five rams, five he-goats, five he-lambs a year old: this was the oblation of Pagiel the son of Ochran. On the twelfth day Ahira the son of Enan, prince of the children of Naphtali: his oblation was one silver platter, the weight whereof was a hundred a thirty [shekels], one silver bowl of seventy shekels, after the shekel of the sanctuary; both of them full of fine flour mingled with oil for a meal-offering; one golden spoon of ten [shekels], full of incense; one young bullock, one ram, one he-lamb a year old, for a burnt-offering; one male of the goats for a sin-offering; and for the sacrifice of peace-offerings, two oxen, five rams, five he-goats, five he-lambs a year old: this was the oblation of Ahira the son of Enan." — Numbers 7:12-83 (ASV)

The various princes make their offerings in the order assigned to the tribes (Numbers 2:0). It was undoubtedly the tribes themselves that presented these gifts through their chiefs. The twelve offerings are exactly alike and were offered on twelve separate days.