The Messenger of Allah ﷺ said, "When Ramadan begins, the gates of mercy are opened, the gates of Hell are shut, and the devils are chained up."
حدثنا يعقوب حدثنا أبي عن صالح قال ابن شهاب حدثني ابن أبي أنس أن أباه حدثه أنه
قال رسول الله ﷺ إذا دخل رمضان فتحت أبواب الرحمة وغلقت أبواب جهنم وسلسلت الشياطين
Its isnad is sahih, despite the error it contains in the name of one of its narrators, just like the preceding one. Yaqub is Ibn Ibrahim bin Saad. Salih is Ibn Kaysan. Muslim related the hadith, 1:297-298, from Muhammad bin Hatim and Hulwani, both of them from Yaqub, from his father, from Salih, from Ibn Shihab, "Nafi bin Abu Anas told me that his father told him that he heard Abu Hurairah..." and so on with the same wording, without stating its text, referring back to what came before it. Nasai likewise related it, 1:299, from Ubaydullah bin Saad bin Ibrahim, from his uncle, who is Yaqub bin Ibrahim bin Saad, with this same isnad, and he explicitly named the narrator as Nafi bin Abu Anas, exactly as in Muslim's version. See what comes later at 7774.