Meaning of “Narrated by the Two Shaykhs”

What is meant by
“the two Shaykhs” is al-Imam al-Bukhari and al-Imam Muslim (may Allah have
mercy on them). 

Al-Bukhari is
Muhammad ibn Isma’eel al-Bukhari (d. 256 AH). He wrote a book, Saheeh
al-Bukhari, in which he compiled a number of saheeh ahadeeth (authentic
prophetic traditions) from our Prophet (peace and blessings of Allah be upon
him). 

Muslim is Muslim
ibn al-Hajjaj al-Nisaboori (d. 261 AH). He is the author of Saheeh Muslim.
These two books – Saheeh al-Bukaari and Saheeh Muslim – are the soundest
books of ahadeeth from our Prophet (peace and blessings of Allah be upon
him). 

If it is said of a
hadeeth (prophetic narration) that it was “narrated by the two Shaykhs”,
what is meant is that it was narrated by al-Bukhari and Muslim in their
Saheehs. The same applies if it says “agreed upon,” i.e., al-Bukhari and
Muslim both agreed on its narration. 

Al-Nawawi (may
Allah have mercy on him) said in the introduction to Sharh Muslim (1/14):
The scholars (may Allah have mercy on them) are agreed that the soundest of
books after the Holy Quran are al-Saheehayn, i.e., the two Saheehs of
al-Bukhari and Muslim, and the ummah (global Muslim community) accepted that
from them. The book of al-Bukhari is the sounder and more useful of the two.
End quote. 

And Allah knows
best.