0 people a very great month has come upon you, a month containing a night better than a thousand months. Allaah has made it an obligation to fast in it, and standing in prayer in its night is a supererogatory action. Whoever seeks nearness to Him with a good deed in it will be like one performing an obligatory action in other months... It is a month the beginning of which is a mercy, the middle Forgiveness, and its end is a granting of freedom from the Fire..."
It is also a long hadeeth; this is the most well-known parts of it. This hadeeth is also reported by lbn Khuzaimah (No.1887), al-Mahaamulee in his Amaalee (No.293), and al-Asbahaanee in at-Targheeb (Q/178, B-manuscript) by way of 'Alee ibn Zayd ibn Jud'aan: from Sa'eed ibn al-Musaayib: from Salmaan.
This isnad (chain) is da'eef (weak) due to the weakness of'Alee ibn Zayd.

Ibn Sad says about him, "He is somewhat weak, he is not used as a proof"
Ahmad ibn Hanbal said: "He is not strong."
Ibn Ma'een said: "He is weak."
Ibn Abee Khaithumah said: "Weak in everything."
Ibn Khuzaimah said: "I do not accept him as a proof due to his weak memory." - as occurs in at-Tahdheeb (7/322-323).
Ibn Khuzaimah said after quoting his narration: "If the narration is authentic."
Ibn Hajr says in al-Atraaf "It is narrated by 'Alee ibn Zayd ibnjud'aan alone and he is weak" as As-Suyootee quotes from him injam'ul-Jawaami' (No.24,714).
Ibn Abee Haatim reports from his father in 'Ilalul-Hadeeth (1/249) that he said: "The hadeeth is munkar (denounced)!"