The Messenger of Allah ﷺ said, "Fast when you see it, and break your fast when you see it. If the month is obscured from you, then count thirty days."
قال رسول الله ﷺ: صوموا لرؤيته، وأفطروا لرؤيته، فإن غمي عليكم الشهر فعدوا ثلاثين.
Bukhari narrated it in the Book of Fasting (1909) and Muslim in the Book of Fasting (19:1081), both of them by way of Shuba, from Muhammad bin Ziyad, who said, "I heard Abu Hurairah say," and then he mentioned it. The wording given here is Muslim's, and Bukhari's wording is similar.As for what has been narrated from Wathila bin Asqa, that the Messenger of Allah said, "The scrolls of Ibrahim were revealed on the first night of Ramadan, the Torah was revealed on the sixth night that had passed of Ramadan, the Injil on the thirteenth night that had passed, and the Quran was revealed on the twenty fourth night that had passed of Ramadan," this is daif. It was narrated by Ahmad (16984), Tabarani in al-Kabir (22/185) and in al-Awsat (3752), Bayhaqi in his Sunan (9/188), in Shuab al-Iman (2248), and in al-Asma wal-Sifat (pp. 233–234), and by Asbahani in al-Targheeb wal-Tarheeb (1818), all of them from the hadith of Imran Qattan, from Qatada, from Abu Malih, from Wathila bin Asqa, who mentioned it. Tabarani said in al-Awsat, "No one narrated this hadith from Qatada except Imran Qattan, and it is not narrated from the Messenger of Allah except through this chain."I say, Imran Qattan is Ibn Dawar, with fatha on the waw followed by ra, known as Abu Awwam, and there is disagreement about him. Ibn Main, Abu Dawud, and Nasai declared him daif. Daraqutni said, "He frequently contradicted others," while others rated him more leniently. However, the rule regarding such narrators is that their hadith cannot be accepted when they narrate alone from a shaykh of extensive narration such as Qatada and others.He was contradicted in the chain by Ubaydullah bin Abu Humayd. This was narrated by Abu Yaala (2195), from Sufyan bin Waki, from his father, from Ubaydullah, from Abu Malih, from Jabir bin Abdullah, as a stopped narration (mawquf). Ubaydullah is Ibn Humayd al-Hudhali, Abu Khattab al-Basri, and he is daif by agreement of the scholars. Hakim and Abu Naeem said, "He narrates unreliable reports (manakir) from Abu Malih and Ataa."It was also narrated by Ibrahim bin Tahman, from Qatada, as his own statement, not attributed further than that, as Bayhaqi stated in al-Asma wal-Sifat. And Ibrahim never met Qatada.There is a corroborating narration (shahid) from the hadith of Ibn Abbas, marfu, "The scrolls were revealed to Ibrahim on the second night of the month of Ramadan, the Psalms (Zabur) were revealed to Dawud on the sixth of Ramadan, the Torah was revealed to Musa on the eighteenth of Ramadan, and the Quran was revealed to Muhammad on the twenty fourth of Ramadan."This was narrated by Ibn Asakir in Tarikh Dimashq (6/202), by way of Tammam bin Muhammad, from Abu Umar Muhammad bin Musa bin Fadala al-Qurashi, who said, narrated to us Abu Qusayy, who said, narrated to us my father, from Ali, that is Ibn Abu Talha, from Ibn Abbas, who mentioned it.Abu Qusayy is Ismail bin Muhammad bin Ishaq bin Ismail al-Udhri. Dhahabi says in al-Siyar (4/185), "The learned scholar of hadith, he narrated from his father, and Tabarani and the hafiz Abu Ali Nisaburi and others narrated from him." As for his father, Ibn Asakir gave his biography in Tarikh Dimashq (52/20) but did not mention anyone who narrated from him other than his son, and did not comment on him either critically or favorably, so he is "unknown in person" (majhul al-ayn).There is another corroborating narration from Ayesha, though it is stopped (mawquf) on her. It was narrated by Khallal in his Amali (32), narrated to us Qadi Abu Hasan Ali bin Hasan al-Jarrahi, narrated to us Muhammad bin Hayawayh al-Marwazi, narrated to us Abdullah bin Hammad al-Amuli, narrated to us Saeed bin Abu Maryam, narrated to us Abdul-Rahman bin Yahya al-Sadafi, Abu Shayba, who said, narrated to me Habban bin Abu Jabala, from Ayesha, who said, "The first scrolls were revealed on the first day of Ramadan, the Torah was revealed on the sixth of Ramadan, the Injil was revealed on the twelfth of Ramadan, the Psalms were revealed on the eighteenth of Ramadan, and the Quran was revealed on the twenty fourth of Ramadan."In this chain is Muhammad bin Hayawayh al-Marwazi. If he is al-Karkhi, then he is accused (of unreliability), and if he is someone else, then I do not know him. The rest of the narrators range between truthful (saduq) and reliable (thiqa).The conclusion is that none of these routes is free from a daif or discarded narrator, or a break in the chain, along with contradictions in both the chain of transmission and the wording.