What exactly did he hear that prompted his joining Moshe and the people of Israel?
The Talmud offers three different possibilities suggested by three different sages. (Massechet Zevachim 116a):
“Rabbi Joshua says, he heard of the war with Amalek and Rabbi Eliezer HaModa’i says, he heard of the giving of the Torah and Rabbi Elazar says, he heard of the splitting of the Red Sea.”
Rashi combines the opinions of Rabbi Joshua and Rabbi Elazar, and sees both the splitting of the Red Sea and the victory over Amalek as being the impactful events that together brought about the spiritual and life implicating changes in Yitro
In the words of Rashi; “Of what did he hear that he came? Of the splitting of the Red Sea and the war against Amalek.”
These were events that changed the world’s perception of G-d (as we see in Exodus 15:14-16 and in the book of Joshua 2:9-11).The Kotsker rebbe asks since he only heard what everybody else heard as well then what made Yitro different? He answers that the whole world was aware that the Jews came out of Egypt with great miracles but they did nothing about it. Yitro, however, heard and he came. He heard and he acted. Yet one must still ask what is it about those two events that would prove so life changing for Yitro. On one level they together were a powerful exposition of G-d’s mastery over nature and over Man.
Reb Simcha Bunim of Psyshcha explains further how each of them represent seemingly differing spiritual directions in this world. The splitting of the red sea represented G-d’s active and miraculous involvement in this world, while the battle with Amalek represented human striving and action that bring about G-d’s Divine intervention.
Yitro was aware of all those pagan beliefs that focused solely on miraculous healings and events. Suddenly he was confronted with community of faith that understood the importance of moving forward in action as a response to faith. In his heart he sensed that this “two way relationship” was truth and therefore” he came”.
Those will be powerful lessons for all those yearning to part of HaShem’s plan of destiny..The first lesson is not to ignore the spiritual and Divinely inspired events around us even if they implicate us to make great personal changes. The second is to understand the necessity and power of our actions and our deeds for they will help bring forward Divine intervention.