When Moses was ordered to number among the Levites all children from a month old and upward, he said to God: "Thou biddest me count them from a month old and upward. Shall I now wander about their courts and houses and count each child, seeing that Thou givest me such a command?" But God replied: "Do thou what thou canst do, and I will do what I can do." It now came to pass that whenever Moses betook himself to a Levite tent he found the Shekinah awaiting him, tell him exactly the number of children without his having to count them.
Moses Protests Counting Every Levite Baby by Hand
Legends of the Jews 4:20