Targum Pseudo-Jonathan on Genesis 9:12 introduces the idea of a sign — an ot — that will anchor the covenant through all time. This is the sign of the covenant which I establish between My Word and between you and every living soul that is with you, unto the generations of the world.
The Aramaic adds the phrase between My Word — bein Memri — to the biblical text. The covenant is not made in some abstract heavenly chamber. It is made between the Memra, the living Word of the Holy One that also spoke the world into being, and every creature that breathes.
And notice the time horizon: unto the generations of the world. Not for a century. Not for Noah and his sons. For as long as the world has generations to count. This is Torah's way of saying: whatever sign is about to be given, it has to be visible to your great-great-great grandchildren, and theirs after them.
The Maggid pauses here before the next verse reveals what the sign will be. A covenant without a sign is easy to forget. A covenant with a visible marker becomes part of the furniture of the world.
The takeaway: when God makes a promise, God also makes a reminder. The reminder is the mercy. Look up — it is coming in the very next verse.