Musnad Ahmad 27:1089

Muhammad narrated to us, Shu'bah narrated to us, from al-Hakam, that he witnessed Sa'id ibn Jubayr stay at Jam' (Muzdalifah). He said: And I think he said: And he gave the adhan, then he prayed Maghrib three rak'ahs, then he gave the taslim, then he prayed Isha two rak'ahs. Then he said: Ibn Umar did for us in this place the same as this. And Ibn Umar said: "The Messenger of Allah (ﷺ) did for us in this place the same as this."