Bulugh al-Maram 133
Narrated Abu Sa'id al-Khudri (RAA):
Two men set out on a journey and when the time of Salat (prayer) came they had no water. They performed Tayammum with clean earth and prayed. Later on they found water within the time of the prayer.  One of them repeated his prayer with ablution but the other did not repeat. Then they came to Allah's Messenger (ﷺ), and related the matter to him. Addressing himself to the one who did not repeat, he said, "You followed the Sunnah and your (first) prayer was enough for you."[9] He said to the one who performed ablution and repeated: "For you there is a double reward".
[Reported by Abu Dawud and An-Nasa'i]
وَعَنْ أَبِي سَعِيدٍ اَلْخُدْرِيِّ ‏- رضى الله عنه ‏- قَالَ: { خَرَجَ رَجُلَانِ فِي سَفَرٍ, فَحَضَرَتْ اَلصَّلَاةَ ‏-وَلَيْسَ مَعَهُمَا مَاءٌ‏- فَتَيَمَّمَا صَعِيدًا طَيِّبًا, فَصَلَّيَا, ثُمَّ وَجَدَا اَلْمَاءَ فِي اَلْوَقْتِ.‏ فَأَعَادَ أَحَدُهُمَا اَلصَّلَاةَ وَالْوُضُوءَ, وَلَمْ يُعِدِ اَلْآخَرُ, ثُمَّ أَتَيَا رَسُولَ اَللَّهِ ‏- صلى الله عليه وسلم ‏-فَذَكَرَا ذَلِكَ لَهُ, فَقَالَ لِلَّذِي لَمْ يُعِدْ: "أَصَبْتَ اَلسُّنَّةَ وَأَجْزَأَتْكَ صَلَاتُكَ" وَقَالَ لِلْآخَرِ: "لَكَ اَلْأَجْرُ مَرَّتَيْنِ" }  رَوَاهُ أَبُو دَاوُدَ, ]و] النَّسَائِيّ ُ  1‏ .‏‏1 ‏- صحيح.‏ رواه أبو داود (338)‏، والنسائي (113)‏.‏