The Messenger of Allah ﷺ said, "When night approaches," and on another occasion he said, "When night comes from this direction and day departs from that direction, the fasting person has broken his fast," meaning the east and the west.
حدثنا وكيع حدثنا هشام بن عروة عن أبيه عروة
قال رسول الله ﷺ إذا أقبل الليل وقال مرة جاء الليل من ههنا وذهب النهار من ههنا فقد أفطر الصائم يعني المشرق والمغرب
Its isnad is sahih. Asim is Ibn Umar bin Khattab. In h, "Hisham bin Urwa, from his father, from Urwa" is an addition made in error, and it will come again with this same isnad at 383. The hadith belongs to the Musnad of Umar, as you can see, but it occurs in Muntaqa under number 2162 attributed to Ibn Umar, and is ascribed there to the Musnad and the Sahihayn, which is a mistake that Shawkani did not point out, at 4/299. The hadith appears in Bukhari, 4/171 of Fath al-Bari, and in Muslim, 1/303, both of them by way of Hisham bin Urwa, from his father, from Asim bin Umar, from Umar.