Nuh (peace be upon him) said : (My Lord! Forgive me, and my parents, and him who enters my home as a believer,) Ad-Dahhak said, “This means, my Masjid.” However, there is no harm in understanding the Ayah according to its apparent meaning, which would be that he (Nuh) supplicated for every person who entered his house who was a believer. Then he said,
(and all the believing men and women.) He supplicated for all of the believing men and women, and that includes those of them who were living and those of them who were dead. For this reason, it is recommended to supplicate like this, in following the example of Nuh, and that which has been reported in the narrations and well-known, legislated supplications.
Source : Tafsir Ibn Kathir
Ubaadah ibn as-Saamit radiallaahu ’anhu related that the Prophet sallallaahu ’alayhi wa sallam said:
“Whosoever seeks forgiveness for the believing men and the believing women, Allaah will record for that person – equivalent to every believing man and believing woman – a good deed.”
Related by al-Haythamî in Majma’az-Zuwaa‘id (l/210) where he said: “The isnaad is jayyid.” [at-Tabarani, classed as Hasan by Al-Albani]
Share this, Baarakallaah Feekum: [“One who guides to something good has a reward similar to that of its doer” - Saheeh Muslim vol.3, no.4665]