Assalamu Alaikum,I have heard a hadith that, "Reading or listening or telling one hadith is equivalent or greater than the reward of 1000 (One thousand) rakah nawfil/mustahab salaah."Now I need to know detail about this. May be this is from book "Fazail e Amal"

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.

Perhaps you are referring to the Hadeeth which Ibn Maajah reported from Abu Tharr . He said:

“The Messenger of Allaah, sallallaahu ‘alayhi wa sallam, said to me, "Abu Tharr, if you set out in the morning and learned one verse from the Book of Allaah, it would be better for you than to pray one hundred Rak'ahs, and if you set out in the morning and learned a matter of knowledge, whether it is acted upon or not, it is better for you than praying one thousand Rak'ahs.”

Al-Munthiri declared the Hadeeth's chain of transmission to be fair in At-Targheeb wat-Tarheeb, but Al-Booseeri declared it weak. Al-Arnaa’oot and other scholars who reviewed the Ahaadeeth in Ibn Maajah's Sunan said: “Its chain of transmission is weak as ‘Abdullaah ibn Ziyaad Al-Bahraani is unidentified and ‘Ali ibn Zayd ibn Jud‘aan is weak. Al-Booseeri also declared the Hadeeth weak in Az-Zawaa'id.” [End of quote]

Al-Albaani also declared it weak.

Furthermore, Shaykh ‘Abdul ‘Azeez Ar-Raajihi said in his commentary on Ibn Majah's Sunan: “This Hadeeth is weak, because ‘Ali ibn Zayd ibn Jud‘aan is weak according to the majority of the scholars. ‘Abdullaah ibn Ziyaad is also weak, so the Hadeeth is weak with this chain of narrators, but its meaning is correct. Acquiring knowledge is better than devoutly worshipping, and this is why the scholars said that acquiring knowledge is better than voluntary acts of worship. That is, a person acquiring knowledge is better than him praying at night or praying the Dhuha prayer, or fasting an optional fast which he is used to fasting, because if optional fasting hinders him from acquiring knowledge, then acquiring knowledge takes precedence to it, because the benefit of knowledge extends to other people (rather than the individual), so if a person learns a matter of knowledge, it is better for him than praying a thousand Rak‘ahs.” [End of quote]

Allaah Knows best.