I accompanied Ibn Umar to al-Hima. When the sun set, I hesitated to remind him of the prayer. He continued traveling until the whiteness of the horizon faded and the darkness of evening had set in. Then he dismounted and prayed Maghrib, three units, followed by two more units after it.He then said, "This is how I saw the Messenger of Allah ﷺ do it."
أخبرني إسحق بن إبراهيم قال أنبأنا سفيان عن ابن أبي نجيح
صحبت ابن عمر إلى الحمى فلما غربت الشمس هبت أن أقول له الصلاة فسار حتى ذهب بياض الأفق وفحمة العشاء ثم نزل فصلى المغرب ثلاث ركعات ثم صلى ركعتين على إثرها ثم قال هكذا رأيت رسول الله ﷺ يفعل
Sahih. Ahmad narrated it in 2/12, and Humaydi in his collection, no. 681 (in my edition), from Sufyan bin Uyayna, through him, and it is also found in Sunan al-Kubra, no. 1570.Ismail here is Ibn Abu Dhuwayb, who is trustworthy, while Ibn Abu Najeeh is known for concealing weaknesses in his chains of transmission, as Nasai stated (Siyar Alam al-Nubala, 7/74), and he transmitted this hadith using the ambiguous formula "from," without specifying direct hearing. The hadith has many supporting witnesses, among them the hadith that follows (596).