Sayyiduna Uqbah bin Amir al-Juhani (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "Whoever performs ablution (wudu) and completes his ablution, then raises his head towards the sky and says: I bear witness that there is no god worthy of worship except Allah, alone, without partner, and that Muhammad is His servant and Messenger, all eight gates of Paradise are opened for him; he may enter through whichever of them he wishes."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14987