How sound is the attribution of the reason for the revelation of Allah’s saying: "And we do not descend except by the command of your Lord," to the Prophet’s asking Gabriel about the reason for his delay, and Gabriel’s replying: "How can I descend upon you while you do not use a toothstick, nor trim your nails, and you do not clean your knuckles?"?

The report inquired about has not been authenticated. It is narrated in some books of Tafsir (definition) from Mujahid that Gabriel delayed coming to the Prophet, peace and blessings be upon him. When he eventually came, the Prophet asked him, "What kept you from me?" He replied, "How can we come to you when you do not trim your nails, nor clean your knuckles, nor trim your mustaches, nor use the miswak?" And he recited: "And we do not descend except by the command of your Lord." This report is not authentic because there is no one who authenticated it, and because the Prophet, peace and blessings be upon him, did not abandon these practices.