These two verses include two parables that Allaah offers about faith in the heart of a believer, and idolatry in the heart of an idolater. Here is As-Sa’di's interpretation of these verses (summarized). He said: "Allaah says {Have you not considered how Allaah presents an example, [making] a good word}, which is the testimony of Laa Ilaaha Illa Allaah (None has the right to be worshipped but Allaah) and its branches, {like a good tree,} namely the palm tree, {whose root is firmly fixed} in the earth {and its branches} are spread {[high] in the sky} and it always gives abundant benefit...{It produces its fruit all the time, by permission of its Lord.}. So is the tree of faith. Its root of knowledge and belief is firmly fixed in the heart of the believer, and its branches of good words, good deeds, pleasing conduct, and good morals are always ascending to Allaah in the heavens. The believer benefits from the actions and words that the tree of faith produces and he benefits others from it...Then Allaah mentioned its opposite, namely the word of disbelief and its branches. He said {And the example of a bad word is like a bad tree,} bad to eat. This is the tree of colocynth and the like, {uprooted from the surface of the earth, not having any stability.}, that is, having no firmness, as it has no veins to hold it and no good fruit to produce; rather, if ever it had any fruit, it is bad fruit. Similarly, the word of Kufr (disbelief) and disobedience is not fixed in the heart to any benefit and does not produce fruits except every evil word and evil deed that harm and does not benefit its doer. No good deed ascends to Allaah from him. He does not benefit himself and he does not benefit others...” [End of quote]