How sound is the Hadith: "Indeed, Allah has an angel entrusted with whoever says: O Most Merciful of the merciful. So, whoever says it three times, the angel says: Indeed, the Most Merciful of the merciful has turned to you, so ask"?

The hadith is weak and not authentic, for it contains Faddal ibn Jubair, who is "not anything" (meaning, his narration is not reliable), and Yazid ibn Aban al-Raqashi, who is "abandoned" (meaning, his narrations are rejected), and al-Fadl ibn Isa, who is "denounced in hadith" (meaning, his narrations are rejected). However, supplicating to Allah using the attribute of mercy is permissible, based on His (the Most High) saying: "Say, 'Call upon Allah or call upon the Most Merciful. Whichever [name] you call upon - to Him belong the best names.'"