It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Holy Prophet (peace and blessings be upon him) said: Whoever performs the funeral prayer in the mosque, his prayer is not valid. The narrator says that when the place would become crowded, the companions would return but would not perform the prayer.

12341 - Waki‘ narrated to us from Ibn Abi Dhi’b from Sa‘id ibn (Ayman) (1) from Kathir ibn (Abbas) (2) who said: I will surely recognize what I have prayed over the funeral in the mosque.

Hazrat Salih narrates from those individuals who witnessed the era of the two Shaykhs; they state that the companions would return when the space in the funeral area became tight, but they would not offer the funeral prayer in the mosque.