Charles Ellicott Commentary Exodus 24:10

"And they saw the God of Israel; and there was under his feet as it were a paved work of sapphire stone, and as it were the very heaven for clearness." — Exodus 24:10 (ASV)

They saw the God of Israel. —Probably, in human form, as Isaiah saw Him (Isaiah 6:1–5), and Ezekiel (Ezekiel 1:26), and even Nebuchadnezzar (Daniel 3:25). It is not of this appearance that Moses says: Ye saw no similitude (Deuteronomy 4:12). The appearance which they saw had “feet.”

A paved work of a sapphire stone. —Heb., a work of the clearness of sapphire. The “sapphire” (sappir) of the Pentateuch is probably lapis lazuli.

The body of heaven —i.e., “the very heaven,” or “the heaven itself.”