Musnad Ahmad 1294:0

Narrated Umm Muslim al-Ashja‘iyyah: The Messenger of Allah (ﷺ) said: "Whoever performs ablution and performs it well, then stands and prays two rak'ahs, focusing upon them with his heart and his face, Paradise will become mandatory for him." She said: I said, "How wonderful this is, O Messenger of Allah!" A narrator who was standing in front of me said, "The one before it was even more wonderful." I looked, and it was Umar ibn al-Khattab. He said, "I have seen you just now, and you said something similar before this." The Prophet (ﷺ) said: "Whoever among you performs ablution and completes the ablution, then says: 'I bear witness that there is no god but Allah alone, with no partner, and I bear witness that Muhammad is His servant and His Messenger,' the eight gates of Paradise will be opened for him, and he may enter through whichever of them he wishes."