The words of Allah: "Fasting has been prescribed for you as it was prescribed for those before you"

Sayyiduna Daghfal bin Hanzalah (may Allah be pleased with him) narrates this saying of the Prophet (peace and blessings be upon him): "The fasts of Ramadan were obligatory upon the Christians. They had a king who fell ill. He vowed that if Allah Almighty cured him, he would add ten days to them. Then after him another man became king over them. He ate meat and fell ill. He said: If Allah Almighty cures him, he will add eight more days of fasting. Then after him another man became their king. He said: However many of these days remain, we will complete them, and we will keep our fasts in the season of spring. Thus their fasts became fifty."
Imam al-Tabarani recorded this narration in al-Mu'jam al-Awsat in this way as a "marfu'" hadith (attributed to the Prophet), as you see, whereas in al-Mu'jam al-Kabir Imam al-Tabarani recorded it as a "mawquf" narration (stopping) at Sayyiduna Daghfal (may Allah be pleased with him). The narrators of both their chains are the narrators of the "Sahih".

Sayyiduna Abu Umamah al-Bahili (may Allah be pleased with him) narrates: I heard the Prophet (peace and blessings be upon him) say: "Indeed, Allah Almighty has made the fasts of Ramadan obligatory upon you, but He has not made the night prayer (qiyam) of Ramadan (that is, Tarawih) obligatory upon you. Its night prayer is something that, if you begin it, you should do regularly, because some people of the Children of Israel introduced an innovation, and Allah Almighty reproached them for abandoning it, saying: 'And monasticism, which they adopted; We had not prescribed it for them; their aim was only to seek the pleasure of Allah Almighty.'" This is to the end of the verse.
Imam al-Tabarani recorded this narration in al-Mu'jam al-Awsat. Its chain contains a narrator, Zakariyya bin Abi Maryam, whom Imam al-Nasa'i (may Allah have mercy on him) and others declared "da'if (weak)".