The Hadith regarding "Ya Sariyya al-jabal", is it authentic or daif or False

Question

Can anyone please give me the reference/source of the following Hadith and let me know the teaching of it:

Sayyidina Abdullah ibn Umar narrates that his father Sayyidina Umar was delivering the Friday sermon in the Prophet’s Masjid in Madinah, when in the middle of the khutba, he shouted, “Ya Sariyya al-jabal! (O Sariyya, [towards] the mountain!” and then he resumed his khutba. When the people had finished the prayer, they asked Sayyidina Umar, and he said, “The idea crossed my mind that the idolaters defeated our brethren and the idolaters would run towards the mountain. So if the Muslims moved towards the mountain, they would have to fight from one side only and if they advanced, they would be destroyed. So those words escaped my mouth, about which you say that you heard these words.”

Answer 1

Well i have found this link with a fatwa of the Saudi-Arabian Fatwa Council which gives sources for the first part of your inquiry:
The words 'Omar (May Allah be pleased with him) shouted "O Sariyya, [towards] the mountain"!
This source only tells what 'Omar shouted and that the Messenger of the army confirmed to 'Omar having heard a voice alerting them with those words!
Adding that this athar أثر as stated is sahih!
Sources for that are:

• fadail as-sahaba فضائل الصحابة of Imam Ahmad,
• dalail an-Nubuwa دلائل النبوة of abu Na'im,
• al muntaqa المنتقى من مسموعاته بمروof ad-Dya',
• tarikh تاريخ دمشق ibn Asakir,
• dalail an-Nubuwa of al-Bayhaqy,
• al-Isabah of ibn Hajr al 'Asqalani (qualified as a hassan narrator chain)
• tarikh البداية والنهاية ibn Kathir also known as al-Bidya wa-Nihyaya (qualified as hassan jayid)
• as-Sawaa'iq al -Muhriqa الصواعق المحرقـة of al-Haytahmy (also qualified as hassan)

And i found a very similar addition to what you have quoted but it seems this is a very weak narration because of the narrator Furat ibn as-Saa'ib فرات بن السائب who is matrok (not trustworthy) this is to be found in usd al-Ghaba أسد الغابة of ibn al-Athyr (65/5). This is from silslat al ahadith as-sahiha (in Arabic), where the scholar al-Albani apparently qualified most of those narrations if not all of them as da'if expect the one narrated by Muhammed ibn 'ijlan محمد بن عجلان via ibn Wahb, which is in al-Bidya wa-Nihaya!

And Allah knows best!