It was narrated that 'Umar bin Al-Khattab said:
"The Messenger of Allah (ﷺ) said: 'Whoever performs Wudu' and does it well, then says: "Ashhadu an la ilaha ill-Allah was ashhadu anna Muhammadan 'abduhu wa rasuluh (I bear witness that there is none worthy of worship except Allah, and I bear witness that Muhammad is his slave and Messenger)," eight gates of Paradise will be opened for him, and he may enter through whichever one he wishes.'"
English reference: Vol. 1, Book 1, Hadith 148
Arabic reference: Book 1, Hadith 149