Abu Dawud and At-Tirmidhi. See also Al-Albani, Mukhtasar Shama'il At-Tirmidhi, p. 47.
Hisnul Muslim 6
For those unfamiliar, Hisnul Muslim (Fortress of the Muslim) is a well-known du'a book compiled by Said Bin Ali Bin Wahf Al-Qahtani. It categorizes authentic supplications that the Prophet ﷺ made in various situations. In the third chapter, "when wearing a new garment" there is 1 supplication mentioned that you can learn and recite when putting on new clothes/garment.
Tips for learning:
We've created a video for each du'a to try and make it easy to learn. There's also transliteration and translation of every du'a. Lastly, after pressing the play button you can tap on any word and it'll skip to that part in the audio.
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