Amr bin Maymun reported,
I witnessed Umar 
pray the dawn prayer at Jam, then he stood and said, "The polytheists used to not depart until the sun had risen, saying, 'Shine forth, Thabir.' But the Prophet ﷺ differed from them and departed before sunrise."
Azami 5144
Sahihعن عمرو بن ميمون يقول
شهدت عمر رضي الله عنه صلى بجمع الصبح، ثم وقف فقال: إن المشركين كانوا لا يفيضون حتى تطلع الشمس ويقولون: أشرق ثبير، وأن النبي ﷺ خالفهم ثم أفاض قبل أن تطلع الشمس.
Bukhari narrated it in the chapter on Hajj (1684), from Hajjaj bin Minhal, who said, Shuba narrated to us, from Abu Ishaq, I heard Amr bin Maymun say (as mentioned above).In a source other than the Sahih, with a sahih chain, the wording is, "Shine forth, Thabir, so that we may hasten." This was narrated by Ibn Majah (3022) and Ahmad and others.His saying, "Shine forth, Thabir," means, enter, O mountain, into the sunrise, just as one says "ajnab," meaning enter into the south, and "ashmal," meaning enter into the north.From this comes His saying, Exalted is He, "So they followed them at sunrise" [Shuara 26:60], meaning they caught up with them at the moment they entered into the sunrise, which is when it rises."Thabir," with a fatha on the tha and a kasra on the ba, is a mountain of Muzdalifa, on the left of one heading toward Mina. It is also said to be the greatest of the mountains of Makkah.His saying, "kayma nughir," means "kay nughir," with the "ma" being extra. "Nughir" means we hasten toward the sacrifice.See Qura by Tabari (pp. 427-428).