Moses observed that the children of Israel were an innumerable host, like the stars of heaven. This was the fulfillment of a promise God had made to Abraham.
One night Abraham was in his tent when God appeared to him in a vision and said, "Do not fear, Abram, I am a shield to you; your reward shall be very great" (Genesis 15:1). Abraham objected that a reward was of little use to him since he had no heir to give it to. Then the LORD took Abraham outside the tent and showed him the myriad stars splayed across the nighttime sky. The LORD said, "Now look toward the heavens, and count the stars, if you are able to count them. ... So shall your descendants be" (Genesis 15:5). It was this promise that Abraham believed and God credited to him as righteousness.
In Deuteronomy 1 the promises God made to Abraham in the Negev were about to be fulfilled. The children of Israel had multiplied into a host that Moses likened to "the stars of heaven in number" (Deuteronomy 1:10).
Though the hosts of Israel might seem innumerable as the stars, God knows each person individually. The Psalms say, "He counts the number of the stars; He gives names to all of them" (Psalm 147:4). With God, no person is inconsequential. He knows each of us by name.
When the people of Israel struggled under the bondage of the Assyrian and Babylonian exile, they felt that God not longer saw them. The people said, "My way is hidden from the LORD, and the justice due me escapes the notice of my God" (Isaiah 40:27). The prophet Isaiah responded by telling the Israelites to look up into the nighttime sky and see the stars:
Lift up your eyes on high and see who has created these stars, the One who leads forth their host by number, He calls them all by name; because of the greatness of His might and the strength of His power, not one of them is missing. (Isaiah 40:26)
If God marshals the starry host, shepherding them so that not even one of them escapes His notice, He also watches over and cares for the people who are like the stars of heaven. Not one of them is missing before Him.