I say, and with God's success: It is not obligatory for him to repeat the prayer, but it is recommended for one who hopes to find water and is confident in finding it to delay his prayer until the end of the time; to perform it in the best manner possible. However, if he does not hope for water, he should not delay the prayer beyond the beginning of the time; because the benefit of waiting is the possibility of finding water, so he performs it with the best of both purifications, which is not available here. Abu Sa'id reported: "Two men went on a journey, and when the time for prayer came, there was no water, so they performed tayammum with clean 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 and mentioned this to him. He said to the one who did not repeat: 'You have followed the Sunnah, and your prayer is valid.' And he said to the one who performed ablution and repeated: 'You have a reward twice.'" This is found in Al-Mustadrak 1: 286, and it was 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-Waqaya p. 112, and Al-Bahr Al-Ra'iq 1: 163-164, and Allah knows best.