Explained by Shaykh Abdur Razzaq Al Badr
Shaykh Abdur Razzaq: The statement of the Prophet عليه الصلاة والسلام:
من استغفر للمسلمين والمسلمات كان له بكل واحد منهم حسنة
Whoever seeks forgiveness for the male and female Muslims, he will receive for himself a good deed for each and every one of them.
Look! Whoever seeks forgiveness for the male Muslims and the female Muslims, he will receive for himself a good deed for each and every one of them. Do you know how many good deeds you will receive if you say in your supplication?!:
اللَّهُمَّ اغفِر لِلْمُسْلِمِينَ والْمُسْلِمَاتِ وَالمُؤمِنِينَ وَالمُؤمِنَاتِ، الأَحيَاءِ مِنهُم وَالأَموَات
O Allah, forgive the male and female Muslims, and the male and female believers, the living and the deceased.
A phrase which is not even one line; how many good deeds will you receive?! Count from Adam until Allah inherits the earth and all those upon it. You will receive a good deed for every Muslim; millions of good deeds. Then you supplicate for them to have guidance, firmness, assistance, success, and safety from trials and tribulations. If this supplication comes from your heart this is proof of the soundness of your heart and conscience for the welfare of your Muslim brother.
Translator’s note: Below is another wording of the Hadith which has been declared Hassan by Shaykh Al Albani
من استغفر للمؤمنين و للمؤمنات كتب الله له بكل مؤمن و مؤمنة حسنة
‘Whoever seeks forgiveness for the believing men and believing women, Allah writes a good deed for him for every believing man and woman.’
(Collected by At Tabarani declared Hassan by Al Albani)
Translated by Rasheed ibn Estes Barbee