When Moses came down Mount Sinai after God gave him directions for the children of Israel he called all of the children of Israel together and spoke to them. How is he able to speak to approximately 3 million people so they could all hear?

That is a good question, because when Scripture says Moses spoke to “all the congregation,” it does not necessarily mean that every individual person was standing within direct earshot of him at the same moment.

Israel was organized through leaders. Exodus 18:21–26 describes rulers over thousands, hundreds, fifties, and tens. Numbers 1:16 and 7:2 also refer to tribal leaders and heads of the people. So when Moses received instructions from God, he could address the elders and representatives, who then communicated those instructions throughout the tribes and families.

We see that pattern explicitly in Exodus 19:7, where “Moses came and called for the elders of the people, and laid before their faces all these words which the LORD commanded him.” The elders then represented and helped communicate with the larger nation.

Also, the estimate of around three million people is not stated directly in Scripture. Exodus 12:37 mentions about 600,000 men besides children, so estimates of the total population vary depending on how wives, children, and others are counted.

There may also have been occasions when very large groups gathered within hearing range, especially with Moses speaking from an elevated place, but the Bible does not require us to imagine millions of people hearing his unaided voice simultaneously.

So the most natural biblical explanation is that Moses communicated God’s instructions through Israel’s organized leadership structure, with elders and tribal leaders helping pass the message to the entire nation.