What exactly, is Hashem telling Moshe in this Pasuk and in the next one?
Rashi: He is telling him that having appeared to the Avos with the Name Keil Shakai and made a covenant with them to save their children from the slavery and to take them to Eretz Cana'an, He was now obligated to fulfill it. 1
Seforno: Besides redeeming Yisrael in order to establish them as His people, Hashem also needed to do so to fulfill the covenant that He has made with the Avos, and because He had heard Yisrael's cries and prayers from their troubles. 2