Narrated by the Shaykh (Al-Mufid), may Allah سبحانه وتعالى support him, through this chain from al-Husayn ibn Sa‘id, from Hammad, from Hariz, from Zurara: I said to Abu Ja‘far عليه السلام: "Can a man perform all the prayers of the night and day with a single tayammum?" Imam عليه السلام said: "Yes, as long as he does not become impure or find water." I said: "If he finds water and expects to reach another source of water, but when he attempts to do so, it becomes difficult for him, what should he do?" Imam عليه السلام said: "This invalidates his tayammum, and he must repeat the tayammum." I said: "If he finds water after beginning the prayer, what should he do?" Imam عليه السلام said: "He should leave the prayer and perform ablution (wudu) if he has not yet bowed (ruku‘). But if he has already bowed, he should continue his prayer, for tayammum is one of the two purifications."