Please verify if this is authentic:
‘When a person hears and replies to the adhan, then reads the du’a after adhan and radina billahi rabba…,he gets two million virtues. And if a lady in the home does this, she gets one million virtues’.
The general virtue of replying to the adhan is proven through authentic (sahih) narrations.
The quotation you have queried seems to be a combination of two narrations.
1) Sayyiduna S’ad ibn Abi Waqqas (radiyallahu ‘anhu) reports that Nabi (sallalahu ‘alayhi wa sallam) said: “Whoever says the following words when he hears the Muadhin will be forgiven”
Ash hadu al la ilaha illalah wahdahu la sharika lah wa anna Muhammadan ‘abduhu wa rasuluh, raditu billahi rabba, wa bi Muhammadin Rasula, wa bil islami dina.
(Sahih Muslim, Hadith: 386)
Some narrations have the words “ Wa ana ash hadu” at the beginning and not just “Ash hadu”.
(Sunan Nasai, Hadith: 1655, Sunan Abi Dawud, Hadith: 525)
2) Sayyidatuna Maymunah (radiyallahu ‘anha) reports that Nabi (sallalahu ‘alayhi wa sallam) once stood between the row of the men and women and said: “O women, when your’ll hear the adhan of this black person and his iqamah, then say just as he said, for verily for each letter, you will be elevated one million stages”. So Sayyiduna ‘Umar (radiyallahu ‘anhu) said : “This is for the women, what about the men”? Nabi (sallalahu ‘alayhi wa sallam) said the men will get double this O ‘Umar…..”
(Al Mu’jamul Kabir, Hadith: 28, volume: 24)
This second narration is very weak and not suitable to quote.
(See Targhib, vol. 1 pg. 186)
And Allah Ta’ala Knows best,
Answered by: Moulana Suhail Motala
Approved by: Moulana Muhammad Abasoomar
Checked by: Moulana Haroon 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.