Can I ask you to please give me a reference to any Ahadith book(sihah-e-sitta) for the following hadith, where I can read the hadith itself. " Abu Hurayrah narrated that the Prophet said: "When you come to the prayer and find us in the position of prostration, you should prostrate with us but do not consider it as a Rak'ah, and whoever joins us in prayer while in Rukoo' (bowing down position) then he has indeed reached the prayer (i.e. his Rak’ah is valid)." [Abu Dawud and Ibn Khuzaymah] "

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

This Hadeeth was reported exclusively by Abu Daawood among the compilers of the main Six Books of Hadeeth. Abu Daawood presents the Hadeeth in the Book of Prayer; the Chapter is entitled, "When the latecomer joins the prayer as the Imaam is prostrating, what should he do?" Hadeeth number 893.

It should be highlighted that not all six Books should be called Sihaah (i.e. containing Saheeh Ahaadeeth only). Among the six, the only ones that include exclusively Saheeh Ahaadeeth are Al-Bukhari and Muslim. Therefore, describing them as "sihaah-e-sitta" is inaccurate. Al-‘Iraaqi said: "And whoever says (the Six Books) are Saheeh absolutely has committed clear  impreciseness."

Allaah Knows best.