Exodus Exodus 20:1-21
Scripture never calls them 'ten commandments' — it calls them the Ten Words (עֲשֶׂרֶת הַדְּבָרִים), the only law God speaks audibly to a whole nation. They open not with a demand but with a recital of redemption already accomplished, are summed up by Jesus in two commands of love, and provoke a terror so great the people beg for a mediator — the very longing YHWH approves and Christ answers.
Exodus Exodus 19
Israel arrives at Sinai already redeemed and is offered, on the far side of the Exodus, to become a kingdom of priests and a holy nation — an offer made conditionally ('if you obey') and in the same chapter fenced off behind a mountain no one, not even the priests, may touch. The holiness that invites also excludes. That tension is the engine of the chapter, and it is resolved only in Christ, in whom the royal priesthood draws near with confidence to Mount Zion, the heavenly Jerusalem.
Leviticus Lev 23:15–22
The Torah commands one feast by counting: seven sabbaths plus one day, from the wave-sheaf of Passover week to the leavened loaves of the fiftieth day. The count matters. The leaven matters. When Acts 2 dates the outpouring of the Spirit to this feast, every detail is already in the book of Leviticus.