‘On the authority of Sayyiduna ‘Abdullah ibn ‘Amr ibnul ‘As (radiyallahu ‘anhuma) that he said, “Whoever fasts ‘Ashura’ it is as if he has fasted the entire year. And whoever gives charity this day it is like the charity of an entire year.” (Ibn Rajab in Lataiful Ma’arif)
Hafiz Ibn Rajab (rahimahullah) has cited this narration as the statement of Sayyiduna ‘Abdullah ibn ‘Amr ibnul ‘As (radiyallahu ‘anhuma). He has referenced it to Abu Musa Al Madini, without citing any part of the chain.
(Lataiful Ma’arif, pg. 102/103, Al Maktabul Islami edition)
I have not come across the chain and could therefore not verify the authenticity.
Imam Ibn Hibban (rahimahullah) has recorded a narration which states that fasting on ‘[Fasting on] Aashura is equivalent to fasting for one year. This part may therefore be quoted.
(Sahih Ibn Hibban; Al Ihsan, Hadith: 3631. See here)
And Allah Ta’ala Knows best.
Answered by: Moulana Suhail Motala
Approved by: Moulana Muhammad Abasoomar
This answer was collected from HadithAnswers.com. The answers were either answered or checked by Moulana Haroon Abasoomar (rahimahullah) who was a Shaykhul Hadith in South Africa, or by his son, Moulana Muhammad Abasoomer (hafizahullah), who is a Hadith specialist.