I say, and with God's success: It is considered that if a person is predominantly inclined to find water if he delays his prayer until the end of the time, it is recommended for him to wait. However, if he prays with tayammum and then finds water while the time is still available, he is not required to repeat the prayer. On the other hand, if he does not expect to find water, he should not delay the prayer beyond the beginning of the time; because the benefit of waiting is the possibility of finding water, thus he performs it with both complete forms of purification, which is not present here. Abu Sa'id (may Allah be pleased with him) reported: "Two men set out on a journey, and when the time for prayer came, there was no water, so they performed tayammum with pure soil, prayed, and then found water during the time. One of them repeated the prayer and the ablution, while the other did not. They came to the Messenger of Allah (peace be upon him) and mentioned this to him. He said to the one who did not repeat: 'You have followed the Sunnah, and your prayer is sufficient for you.' And he said to the one who performed ablution and repeated: 'You have a reward twice.'" This is reported in Al-Mustadrak 1: 286, and it is authenticated, and in Sunan Al-Darimi 1: 207, Sunan Al-Bayhaqi Al-Kabir 1: 231, Sunan Abu Dawood 1: 93, and Al-Mujtaba 1: 213. See: Sharh Al-Wiqayah p. 112, and Al-Bahr Al-Ra'iq 1: 163-164, and Allah knows best.