Seforno: It is written with reference to the Tefilos offered up by the Tzadikim of the generation. ¹

Targum Onkelos and Targum Yonasan: It means that Hashem paid heed to their complaints.

Rashbam: He promised each of the Avos that He would give their children Eretz Kena'an, and the four hundred years that He told Avraham the Galus would last had almost come to an end.

Seforno: He remembered the covenant that He made with Avraham, ¹ to be for him a G-d and for His children after him, which He acts upon whenever we cry out to Him. ²