"How does the Lord regard the using of the presses in His institutions to print the errors of the enemy? When objectionable matter is mingled with sacred matter coming from the presses, His blessing cannot rest upon the work done. Said the divine Teacher: “What have you gained by bringing in this outside work? It has brought you much vexation of spirit; and the workers have had to hurry and rush to get the matter finished in the specified time. This has occasioned confusion and strife. Harsh words have been spoken, and an unpleasant spirit has been brought into the office. The financial gain in no way compares with the loss which has come through rushing and driving and scolding and fretting.” 8T 88.4"
"Be ye not unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? and what communion hath light with darkness?"
The EGW passage directly addresses the principle of not mixing sacred and secular, which aligns with the idea of not being unequally yoked with unbelievers. The EGW passage speaks against mixing 'objectionable matter' with 'sacred matter,' which is a specific application of the broader principle in 2 Corinthians 6:14.