📖 Thawban RadhiAllahu 'anhu narrated: Allah's noble Messenger Muhammad SallAllahu 'alaihi wa sallam said, "Remain upright (steadfast, firm upon the truth) though you cannot encompass it entirely. Know that the best of your good deeds is the prayer and that none preserves his ablution but a believer (only the true believers strive to perform wudhu/ablution as properly as they can)."
Source: Sunan Ibn Mājah 277
Grade: Sahih (Authentic) according to Al-Albani
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