Yaakov initially doesn’t believe that Yosef is alive. But the image of the wagons convinces him.

The last conversation between Yaakov and Yosef before Yosef gets sold as a slave, becomes the catalyst for all of Jewish history.

Gemara Brachos 31 A

Bereishis Perek 37 Possuk 14 Commentery of Rashi and Baal Haturim

Midrash Movoi Tanchuma Chapter 66

Bereishis Perek 46 Pesukim 26 and 27.

Commentery of Rashi on Possuk 27

Midrash Rabba Bereishis 94 3