Overall meaning : Almighty Allah says: Do you not know, Muhammad, how Allah likens a good word—namely the statement affirming pure monotheism ‘There is no god worthy of worship except Allah’—to a good tree, whose roots are firmly planted in the ground and its branches soar up into the sky, yielding its abundant, fine produce at all times by its Lord’s permission? The good word, just like the good tree, also continues to yield the believer’s good deeds at all times, which ascend to Allah at any time of the day or night and He accepts them. Thus does Allah set forth parables for people so that they may reflect on them, understand what He wants them to know, and do what He commands and avoid what He forbids.
But an evil word—the word of unbelief—is like a foul-tasting tree that is uprooted from the face of the earth, with no roots to hold it firm and strong, nor any branches whatsoever reaching into the sky, nor does it bear any fruit or have any benefit at all. The unbelievers’ unbelief, just like the evil word, neither stays firm, nor is there any good in it, nor does it yield any benefit, nor do the good deeds the unbelievers do ascend to Allah, nor does Allah accept them. Allah makes the believers steadfast with the firm word—namely the testimony of faith ‘There is no god worthy of worship except Allah and Muhammad is Allah’s Messenger’—which is firmly established in their hearts; He makes them steadfast with it in the life of this world by making their faith firm, at the time of their death by granting them a good ending and in the grave at the time when the two angels question them about their Lord, their religion and their Prophet and they respond correctly; and He leads the unbelievers and hypocrites astray for having wronged themselves. Allah does whatever He wills by guiding and strengthening the faithful and leading the wrongdoers astray.