Question Summary:
When did the battle of Khaibar take place and how many Sahabah took part?

Question Detail:

Can you please give reference for hadith where it is mentioned the prophet said khaybar khaybar ya yahood, is it mentioned in Hadith?
In which year did the battle of khaybr take place and how many sahabah took part in that battle?

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
Hereunder is the Hadith you enquire about,
عَنْ أَنَسٍ ـ رضى الله عنه أَنَّ النَّبِيَّ صلى الله عليه وسلم خَرَجَ إِلَى خَيْبَرَ فَجَاءَهَا لَيْلاً، وَكَانَ إِذَا جَاءَ قَوْمًا بِلَيْلٍ لاَ يُغِيرُ عَلَيْهِمْ حَتَّى يُصْبِحَ، فَلَمَّا أَصْبَحَ، خَرَجَتْ يَهُودُ بِمَسَاحِيهِمْ وَمَكَاتِلِهِمْ، فَلَمَّا رَأَوْهُ قَالُوا مُحَمَّدٌ وَاللَّهِ، مُحَمَّدٌ وَالْخَمِيسُ‏.‏ فَقَالَ النَّبِيُّ صلى الله عليه وسلم ‏ "‏ اللَّهُ أَكْبَرُ، خَرِبَتْ خَيْبَرُ، إِنَّا إِذَا نَزَلْنَا بِسَاحَةِ قَوْمٍ فَسَاءَ صَبَاحُ الْمُنْذَرِينَ ‏"‏‏.‏
Anas (Radhiallahu anhu) narrates: The Prophet (Sallalahu Alahi Wa Sallam) set out for Khaibar and reached it at night. He used not to attack if he reached the people at night, till the day broke. So, when the day dawned, the Jews came out with their bags and spades. When they saw the Prophet; they said, "Muhammad and his army!" The Prophet (Sallalahu Alahi Wa Sallam) said, Allahu--Akbar! (Allah is Greater) and Khaibar is ruined, for whenever we approach a nation (i.e. enemy to fight) then it will be a miserable morning for those who have been warned." (Bukhari 2945)
The battle of Khaibar took place in the seventh year after Hijrah in the month of Muharram, about twenty days after the return of Rasulullah (Sallalahu Alahi Wa Sallam) from the battle of Hudaibiyah.[1]
The number of Sahabah that took part in the battle of Khaibar was 1400, including 200 cavalries. There were also a number of women from the Sahabiyaat also went along with the Muslims, to look after the sick and the wounded as well as to prepare food for the men.[2]
 
And Allah Ta’āla Knows Best
Arshad Ali
Student Darul Iftaa
Trinidad
Checked and Approved by,
Mufti Ebrahim Desai.
http://www.daruliftaa.net/