Thawban reported: The Messenger of Allah, peace and blessings be upon him, said, “Remain upright, though you cannot encompass it entirely. Know that the best of your good deeds is prayer and that none can preserve his ablution but a believer.”
Source: Sunan Ibn Mājah 277
Grade: Sahih (authentic) according to Al-Suyuti
Al-Nawawi said, “Our scholars agreed upon the recommendation to renew ablution, which is that one with ablution later performs it again, without having lost his ritual purification.”
Source: al-Majmū’ Sharḥ al-Muhadhab 1/469
عَنْ ثَوْبَانَ قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ اسْتَقِيمُوا وَلَنْ تُحْصُوا وَاعْلَمُوا أَنَّ خَيْرَ أَعْمَالِكُمْ الصَّلَاةَ وَلَا يُحَافِظُ عَلَى الْوُضُوءِ إِلَّا مُؤْمِنٌ
277 سنن ابن ماجه كتاب الطهارة وسننها باب المحافظة على الوضوء
988 المحدث السيوطي خلاصة حكم المحدث صحيح في الجامع الصغير
قال النووي اتَّفَقَ أَصْحَابُنَا عَلَى اسْتِحْبَابِ تَجْدِيدِ الْوُضُوءِ وَهُوَ أَنْ يَكُونَ عَلَى وُضُوءٍ ثُمَّ يَتَوَضَّأُ مِنْ غَيْرِ أَنْ يُحْدِثَ
1/469 المجموع شرح المهذب