On the second day after the Israelites arrived at Sinai, Moses ascended the mountain to meet God (Exodus 19:3). The Mekhilta notes a crucial detail: God called out to Moses before speaking to him. This establishes a principle — the calling always preceded the speaking. God did not simply begin issuing commands. He first summoned Moses by name, showing respect and establishing readiness before delivering the message.
God then instructed Moses with a specific phrase: "Thus shall you say to the house of Jacob." The Mekhilta unpacks the word "thus" (koh) four different ways, each revealing a layer of obligation placed on Moses as the intermediary between God and Israel.
First, "thus" means in the holy tongue — Moses must deliver the message in Hebrew, the sacred language. The words of Sinai were not to be paraphrased into any other language; they carried inherent sanctity in their original form. Second, "thus" means in this order — Moses had to preserve the exact sequence of God's words, not rearranging or restructuring the message for convenience. Third, "thus" means on this matter — Moses was to stay on topic, conveying precisely what God intended, nothing tangential or interpretive. Fourth, "thus" means that Moses must not subtract from the message and must not add to it. He was a faithful transmitter, not an editor.
These four constraints reveal the rabbinic understanding of prophecy itself. Moses did not merely receive inspiration. He received precise language, in a precise order, on a precise subject, and was forbidden from altering a single element. The word "thus" became a boundary marker for prophetic authority.