"Then this map was removed and another put in its place. On it light was shining from a few places only. The rest of the world was in darkness, with only a glimmer of light here and there. Our Instructor said: “This darkness is the result of men's following their own course. They have cherished hereditary and cultivated tendencies to evil. They have made questioning and faultfinding and accusing the chief business of their lives. Their hearts are not right with God. They have hidden their light under a bushel.” 9T 29.1"
"Neither do men light a candle, and put it under a bushel, but on a candlestick; and it giveth light unto all that are in the house."
The EGW passage directly quotes and applies the concept of hiding one's light under a bushel from Matthew 5:15.