Where did the israelites get their animals and grain for sacrifice in the desert

Just finished reading the Book of Numbers. Like Leviticus, the book before it, these books describe in details the sacrificial system given to the Israelites as they travelled through the desert. Up until now I had always thought that the Israelites had been stubborn, ungrateful, and unfaithful. They had the privilege of seeing God's miracles every single day - manna from heaven and quails coming out of nowhere to provide food for their journey (Exodus 16:31), cloud by day to shield them from the desert sun and fire by night to keep them warm (Exodus 13:21), and being shown the glory of God from time to time (Numbers 16:42)! But such is human nature. The sad end to the entire generation of Israelites aged twenty years and over, who left Egypt (and slavery) by God's mighty hand, would perish in the desert without entering the promised land. The apostle Paul reminded us that these things happened to them as examples and as warnings for us (1 Corinthians 10:11).

But thinking from the perspective of the Israelites, what was it that made believing in God so difficult? For one thing, the sacrificial system was very hard! The Skeptics estimated that over the 40-year period, there would have been 1,007,400 lambs and 3,007,600 pigeons or turtledoves sacrificed. These animals were presumably taken from Egypt when they left (Exodus 12:35-36). But what about the grain that was required for offering? Where did they get that in the desert?

Bible.org "The Grain Offering" offered a very scholastic explanation. The "grain" that was offered was likely "seeds" that the Israelites took from Egypt in order to restart farmland wherever the Israelites would end up. So that would be their security that they were to offer up! So it would be like giving up our retirement savings!

Jesus told his disciples, “If anyone would come after me, let him deny himself and take up his cross and follow me. For whoever would save his life will lose it, but whoever loses his life for my sake will find it. For what will it profit a man if he gains the whole world and forfeits his soul? Or what shall a man give in return for his soul? (Matthew 16:24-26)

Again, the story of the rich young man who came to Jesus to ask him "What must I do to inherit eternal life?" (Mark 10:17-31). Jesus' reply: “You lack one thing: go, sell all that you have and give to the poor, and you will have treasure in heaven; and come, follow me.”. Disheartened by the saying, he went away sorrowful, for he had great possessions.

I continue to see God's miracles every single day. I sometimes feel that I am giving away too much for God. I must continue to learn from scripture. Romans 8:31-37 is particularly helpful. Here is my favourite verse to put things into perspective:
He who did not spare his own Son but gave him up for us all, how will he not also with him graciously give us all things? (verse 32)