And behold, the Vilna Gaon did not explain what the "great wealth" given to them after the Exodus from Egypt was. Simply put, it refers to the spoils of the sea that Israel received after the splitting of the Red Sea. Indeed, it can be said further that it refers to the Torah, which they were destined to receive at Mount Sinai. This is similar to what is stated in the Gemara (Ketubot 50a): "'Wealth and riches are in his house, and his righteousness endures forever' (Psalms 112:3). Rav Huna and Rav Chisda, one said, this refers to one who learns Torah and teaches it, and the other said, this refers to one who writes Torah, Prophets, and Writings and lends them to others." We see that the study of Torah is called "wealth and riches," and therefore it can be said that the "great wealth" that Hashem told Abraham about hints at the receiving of the Torah.