Parashas Vayechi · Passuk 48:7
And as for me, when I came from Paddan, Rachel died unto me in the land of Kenaan in the way, when there was still some way to come unto Efras; and I buried her there in the way of Efras — the same is Beis-Lechem.
Torah Temimah points to Yerushalmi Shabbos 6:9 (and parallel Bavli Chullin 95b).
TT lemma: ואני בבאי מפדן.
English: R’ Eliezer ben Yaakov taught: “Ye shall not practice divination nor soothsaying” — even though there is no divination, there is a sign, provided it is after three signs; for example: “And as for me, when I came from Paddan, Rachel died unto me \ldots Yosef is not, and Shimon is not.”
Asmachta from the narrative — the triple occurrence of misfortune supplies the model for distinguishing a permitted siman from prohibited divination.
One may take note of a pattern of three successive events as a siman, but may not practice or rely upon divination. The verse supplies the classic illustration of three signs.