"Aaron and Hur, took his position on a hill overlooking the battlefield. There the man of God laid the case before Him who alone was able to give them the victory. With hands outstretched toward heaven, Moses prayed earnestly for the success of the armies of Israel. It was observed that while his hands were reaching upward, Israel prevailed against the foe; but when through fatigue they were allowed to fall, Amalek prevailed. Aaron and Hur stayed up the hands of Moses until victory, full and complete, turned upon the side of Israel and their enemies were driven from the field. 4T 530.3"
"And it came to pass, when Moses held up his hand, that Israel prevailed: and when he let down his hand, Amalek prevailed."
The EGW passage directly recounts and interprets the events described in Exodus 17:11, making it a clear and explicit allusion.