Is the Hadith in which Allah says, "Write down much of My mercy for My servant" when the servant says "Subhan Allah" (Glory be to Allah) and "Alhamdulillah" (Praise be to Allah), and He says, "Write down much of My love for My servant" when the servant says "La ilaha illa Allah" (There is no god but Allah), authentic?

This narration was transmitted by Al-Tabarani, Ibn Abi Shaybah, and Ibn Fudayl Al-Dabbi. Its chain of transmission revolves around Atiyah ibn Sa'd Al-Awfi, who is considered weak by the imams of Hadith. There is a discrepancy in his narration: sometimes he narrates it as marfu' (attributed to the Prophet, peace be upon him) and sometimes as mawquf (attributed to Abu Sa'id, may Allah be pleased with him). Al-Daraqutni stated that this discrepancy is from Mis'ar, not from Atiyah. Sheikh Al-Albani graded this Hadith as hasan li ghayrihi (good due to external corroboration).

The meaning of the Hadith is that when a servant says: "Subhanallah (Glory be to Allah)," or "Alhamdulillah (Praise be to Allah)," or "Allahu Akbar (Allah is the Greatest)," or "La ilaha illa Allah (There is no god but Allah)," Allah commands the angels to record abundant mercy for him. And if he says: "La ilaha illa Allah," Allah commands the recording of His love for him.