Rabbi Yitzchak

Rabbi Yitzchak was a rabbi who lived in the 3rd century in the Land of Israel.
He was likely a student of Rabbi Yochanan.
There existed several rabbis of this name. According to Rashi and Rashbam, the Rabbi Yitzchak who taught aggadah was named Yitzchak ben Pinchas, while the Rabbi Yitzchak who taught halacha was named Yitzchak ben Acha. Another Rabbi Yitzchak was the student of Rabbi Hiyya.

Teachings

Rabbi Yitzchak transmitted laws in the names of Rabbi Yochanan, Reish Lakish, and others. Laws in his name were transmitted by Rav Nachman, Rav Chisda, Rav Yosef, Rava, and others. He is known for the principle "A person handles his wallet at all times", according to which if one finds money in a public area, one may presume the owner had already noticed the absence and given up the money's ownership out of despair.
He was a colleague of Rav Nachman, and his blessing to Rav Nachman is well known: