"During the forty years after the flight of Moses from Egypt, idolatry seemed to have conquered. Year by year the hopes of the Israelites grew fainter. Both king and people exulted in their power, and mocked the God of Israel. This grew until it culminated in the Pharaoh who was confronted by Moses. When the Hebrew leader came before the king with a message from “Jehovah, God of Israel,” it was not ignorance of the true God, but defiance of His power, that prompted the answer, “Who is Jehovah, that I should obey His voice? ... I know not Jehovah.” From first to last, Pharaoh's opposition to the divine command was not the result of ignorance, but of hatred and defiance. PP 333.1"
"And Pharaoh said, Who is the Lord, that I should obey his voice to let Israel go? I know not the Lord, neither will I let Israel go."
The EGW passage directly quotes and elaborates on Exodus 5:2, making it a clear explicit allusion.