וְהָיָה֩ כִֽי־יָבֹ֨אוּ עָלֶ֜יךָ כָּל־הַדְּבָרִ֣ים הָאֵ֗לֶּה הַבְּרָכָה֙ וְהַקְּלָלָ֔ה אֲשֶׁ֥ר נָתַ֖תִּי לְפָנֶ֑יךָ וַהֲשֵׁבֹתָ֙ אֶל־לְבָבֶ֔ךָ בְּכָל־הַגּוֹיִ֔ם אֲשֶׁ֧ר הִדִּיחֲךָ֛ יְהוָ֥ה אֱלֹהֶ֖יךָ שָֽׁמָּה׃
Und es wird geschehen, wenn all diese Dinge über dich kommen, der Segen und der Fluch, die ich dir gegeben habe, und du sollst unter allen Völkern denken, wohin der Herr, dein Gott, dich getrieben hat.
Ramban on Deuteronomy
AND IT SHALL COME TO PASS, WHEN ALL THESE THINGS ARE COME UPON THEE. I have already mentioned47See Leviticus 26:12, and above, 4:25; 19:8. that this chapter refers to the future, for all its subjects have not happened and have not been created, but they are destined to take place.
Sforno on Deuteronomy
והשבות אל לבבך, you will be able to distinguish the truth between apparently contradictory phenomena. When you become the victim of what has been predicted for the sinners, you will realise how far you had strayed from G’d’s Torah, i.e. from G’d Himself.
Or HaChaim on Deuteronomy
והיה כי יבאו עליך כל הדברים, "It will be when all these things will come upon you, etc." Why did the Torah speak about "all these things," instead of merely writing: "when the blessing or curse will come upon you?" ...