TT #787 · Parashas Ki Seitzei · Seventh Aliyah · Passuk 25:18
how he happened upon you on the way and cut down all the stragglers in your rear, when you were weary and exhausted, and he did not fear God.
Torah Temimah points to Sifrei.
TT lemma: אֲשֶׁר קָרְךָ.
אֲשֶׁר קָרְךָ – אֵין קָרְךָ אֶלָּא נִזְדַּמֵּן לְךָ.
English: “Who happened upon you” — “happened” means nothing other than that he encountered you (by chance / by design).
On the daf / in context: The verb is taken in its plain sense of an encounter, not in the midrashic sense of ritual impurity sometimes associated with the root.
Derash on the plain meaning of the verb.
Amalek deliberately (or opportunistically) encountered Israel on the way.