A.B. Simpson emphasizes the concept of spiritual separation in his sermon 'The God of Israel Hath Separated You.' He illustrates how a plant can thrive in unclean surroundings while its roots remain untouched by filth, symbolizing the believer's call to be separate from worldly desires and influences. Simpson argues that true separation is not merely about abstaining from sinful activities but involves a heart that does not long for those things. The essence of holiness is found in a genuine detachment from the love of the world, which defiles the soul. The true Levite, he asserts, is one who has no desire for earthly pleasures, reflecting a heart wholly devoted to God.

The little plant may grow out of a pile of refuse and be surrounded by filth and covered with the dust that floats on the breeze, but its white roots are separated from the unclean soil, and it leaves and flowers have no affinity with the dust that settles upon them. After a show of summer rain they throw off every particle of defilement and look up as fresh and spotless as before. Their intrinsic nature cannot have any part with these defiling things. This is the separation which Christ requires and which He gives. There is no merit in my staying from the theater is I want to go. There is no value in my abstaining from the foolish novel or the intoxicating bottle if I am continually wishing I could have them. My heart is there, and my soul is defiled by the desire for evil things. It is not the world that stains us, but the love of the world. The true Levite is separated from the desire for earthly things, and even if he could, he would not have the forbidden pleasures which others prize.