Is it true that David (peace be upon him) prostrated for forty days until grass grew beneath him, and that was when he committed the sin?

This narration about David (peace be upon him) is among the Isra'iliyyat (Judeo-Christian traditions) transmitted by the exegetes. Nothing in it has been authentically reported from the Messenger of Allah (peace and blessings of Allah be upon him). The type of tribulation that afflicted David (peace be upon him) has no authentic narration from the Messenger of Allah (peace and blessings of Allah be upon him). Ibn Kathir believes that it is more appropriate to merely recite this story and refer its knowledge to Allah Almighty. Similarly, Al-Shanqiti holds that much of what many exegetes mention in their interpretation of this noble verse, which is inconsistent with the stature of David (peace be upon him), all traces back to the Isra'iliyyat, and thus cannot be trusted or relied upon. And whatever of it has been attributed to the Prophet (peace and blessings of Allah be upon him) is not authentic.