The forty days that Moses spent in heaven were entirely devoted to the study of the Torah, he learned the written as well as the oral teaching, yea, even the doctrines that an able scholar would some day propound were revealed to him. He took an especial delight in hearing the teachings of the Tanna Rabbi Eliezer, and received the joyful message that this great scholar would be one of his descendants.
The study of Moses was so planned for the forty days, that by day God studied with him the written teachings, and by night the oral. In this way was he enabled to distinguish between night and day, for in heaven "the night shineth as the day." There were other signs also by which he could distinguish night from day; for if he heard the angels praise God with "Holy, holy, holy, is the Lord of hosts," he knew that it was day; but if they praised Him with "Blessed be the Lord to whom blessing is due," he knew it was night. Then, too, if he saw the sun appear before God and cast itself down before Him, he knew that it was night; if, however, the moon and the stars cast themselves at His feet, he knew that it was day. He could also tell time by the occupation of the angels, for by day they prepared manna for Israel, and by night they sent it down to earth. The prayers he heard in heaven served him as another token whereby he might know the time, for if he heard the recitation of the Shema' precede prayer, he knew that it was day, but if the prayer preceded the recitation of the Shema', then it was night.