The Messenger of Allah ﷺ taught her this supplication, "O Allah, I ask You for all that is good, both what comes soon and what is delayed, what I know of it and what I do not know. O Allah, I ask You for the best of what Your servant and Prophet Muhammad ﷺ asked of You, and I seek refuge in You from the worst of what Your servant and Prophet sought refuge from. O Allah, I ask You for Paradise and for whatever brings me near to it, in word or deed, and I ask You to make every decree You ordain for me a good one."
حدثنا عفان قال حدثنا حماد قال أخبرنا جبر بن حبيب عن أم كلثوم بنت أبي بكر
أن رسول الله ﷺ علمها هذا الدعاء اللهم إني أسألك من الخير كله عاجله وآجله ما علمت منه وما لم أعلم اللهم إني أسألك من خير ما سألك عبدك ونبيك محمد ﷺ وأعوذ بك من شر ما عاذ منه عبدك ونبيك اللهم إني أسألك الجنة وما قرب إليها من قول أو عمل وأسألك أن تجعل كل قضاء تقضيه لي خيرا
Its isnad is sahih. Jabr bin Habib is trustworthy, one of the scholars of language, and Umm Kulthum is the sister of Ayesha. Whoever said there is doubt about her erred, for what they actually said was that there is doubt about her companionship. The hadith was narrated by Ibn Majah 2/1264, no. 3846, and Bukhari in Adab al-Mufrad 639, and Ibn Hibban 598, no. 2413, Mawarid, and Hakim graded it sahih 1/521, and Dhahabi agreed with him.