John Gill Commentary Numbers 7:87

"all the oxen for the burnt-offering twelve bullocks, the rams twelve, the he-lambs a year old twelve, and their meal-offering; and the males of the goats for a sin-offering twelve;" — Numbers 7:87 (ASV)

All the oxen for the burnt offering [were] twelve bullocks ,
&c.] According to the number of the princes and their tribes, and so,

the rams twelve, the lambs of the first year twelve ;
which were also for the burnt offering:

with their meat offering ;
which always went along with the burnt offering:

and the kids of the goats, for a sin offering, twelve ;
thus the twelve princes, and by them the twelve tribes, expressed their faith in Christ, the antitype of those sacrifices, and their hope of his coming into the world to be a sacrifice for sin, and of their atonement, reconciliation, peace, pardon, and salvation by him; see (Acts 26:6Acts 26:7) .