The Messenger of Allah ﷺ used to say, "O Allah, You have made my form beautiful, so beautify my character as well."
أن رسول الله ﷺ كان يقول: اللهم أحسنت خلقي فأحسن خلقي.
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Ahmad (3823), Tayalisi (372), and Bayhaqi in Shuab (8183) narrated it, and Ibn Hibban (959) graded it sahih, all of them through routes from Asim bin Sulayman Ahwal, from Awsaja bin Rimah, from Abdullah bin Abu Huzayl, from Abdullah bin Masud, who narrated it as mentioned.Its chain is hasan because of Awsaja bin Rimah, for he is hasan al-hadith. Ibn Main deemed him trustworthy, and Ibn Hibban listed him among the trustworthy narrators. As for Daraqutni, he said, "He is close to unknown, no one narrates from him except Asim, he cannot be relied upon as proof, but he may be considered as corroborating evidence."It has also been narrated from Asim with this chain as a stopped report attributed only to Ibn Masud, though the narrators who reported it as a raised report are more numerous. Asim also narrated it from Abdullah bin Harith, from Ayesha, as mentioned previously. So perhaps the hadith was known to Asim through two chains, and Allah knows best.As for what has been narrated from Ayesha, that she said, "When the Messenger of Allah ﷺ looked at his face in the mirror, he would say, 'Praise be to Allah, O Allah, You have made my creation good, so make my character good,'" its chain is very daif.Abu Shaykh narrated it in Akhlaq an-Nabi ﷺ (148) through the route of Aban bin Sufyan, from Abu Hilal, and Bayhaqi in Daawat (489) through the route of Maslama, both of them (Abu Hilal and Maslama) narrating from Hisham bin Urwa, from his father, from Ayesha, who narrated it as mentioned. Aban bin Sufyan is matruk (his narrations are abandoned), and Maslama is Ibn Ali Khushani, who is likewise matruk.This supplication upon looking in the mirror has also been narrated through the hadith of Ali bin Abu Talib, Ibn Abbas, and Anas bin Malik, but all of these are very daif.