"The Lord hearkened to his prayer, and directed him to summon seventy men of the elders of Israel—men not only advanced in years, but possessing dignity, sound judgment, and experience. “And bring them unto the tabernacle of the congregation,” He said, “that they may stand there with thee. And I will come down and talk with thee there: and I will take of the spirit which is upon thee, and will put it upon them; and they shall bear the burden of the people with thee, that thou bear it not thyself alone.” PP 380.1"
"And the Lord said unto Moses, Gather unto me seventy men of the elders of Israel, whom thou knowest to be the elders of the people, and officers over them; and bring them unto the tabernacle of the congregation, that they may stand there with thee."
EGW directly quotes Numbers 11:16 and provides context, explaining the reason for selecting seventy elders to assist Moses. This is a clear and direct reference.
"The Lord permitted Moses to choose for himself the most faithful and efficient men to share the responsibility with him. Their influence would assist in holding in check the violence of the people, and quelling insurrection; yet serious evils would eventually result from their promotion. They would never have been chosen had Moses manifested faith corresponding to the evidences he had witnessed of God's power and goodness. But he had magnified his own burdens and services, almost losing sight of the fact that he was only the instrument by which God had wrought. He was not excusable in indulging, in the slightest degree, the spirit of murmuring that was the curse of Israel. Had he relied fully upon God, the Lord would have guided him continually and would have given him strength for every emergency. PP 380.2"
"Moreover thou shalt provide out of all the people able men, such as fear God, men of truth, hating covetousness; and place such over them, to be rulers of thousands, and rulers of hundreds, rulers of fifties, and rulers of tens:"
The EGW passage expands on the idea of choosing leaders and the potential pitfalls, directly relating to the context of Exodus 18:21.
"Moses was directed to prepare the people for what God was about to do for them. “Sanctify yourselves against tomorrow, and ye shall eat flesh: for ye have wept in the ears of the Lord, saying, Who shall give us flesh to eat? for it was well with us in Egypt: therefore the Lord will give you flesh, and ye shall eat. Ye shall not eat one day, nor two days, nor five days, neither ten days, nor twenty days; but even a whole month, until it come out at your nostrils, and it be loathsome unto you: because that ye have despised the Lord which is among you, and have wept before Him, saying, Why came we forth out of Egypt?” PP 380.3"
"And say thou unto the people, Sanctify yourselves against to morrow, and ye shall eat flesh: for ye have wept in the ears of the Lord, saying, Who shall give us flesh to eat? for it was well with us in Egypt: therefore the Lord will give you flesh, and ye shall eat."
The EGW passage directly quotes Numbers 11:18, making it a clear explicit allusion.