It is narrated from Sayyiduna Umar (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: Whoever performs ablution and performs it well, then raises his gaze towards the sky and recites this supplication: "I bear witness that there is no god but Allah, He is alone, He has no partner, and I bear witness that Muhammad is His servant and Messenger," then all eight gates of Paradise will be opened for him, and he may enter through whichever one he wishes.
Benefits: … The words "then he raised his gaze towards the sky" are not present in Sahih Muslim; investigate further. In Jami‘ at-Tirmidhi, the complete supplication is as follows: "Ashhadu an la ilaha illa Allahu wahdahu, la sharika lahu, wa ashhadu anna Muhammadan abduhu wa rasuluhu, Allahumma aj‘alni min at-tawwabeen waj‘alni min al-mutatahhireen." I bear witness that there is no deity worthy of worship except Allah, He is alone and has no partner, and I bear witness that Muhammad (sallallahu alayhi wa sallam) is His servant and Messenger. O Allah, make me among those who repent much and make me among those who keep themselves pure.