Sayyiduna Ibn Mas'ud (may Allah be pleased with him) was teaching a man the Qur'an. When they reached the bank of the Euphrates, he urinated, and the man stopped reciting. Sayyiduna Ibn Mas'ud (may Allah be pleased with him) said: "What is the matter?" He said: Your ablution has been broken. He said: "Recite." So he began to recite, and he kept prompting him whenever he faltered.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8692