Al-Bukhaari (1149) and Muslim (2458) narrated from Abu Hurayrah that the Prophet (blessings and peace of Allah be upon him) said to Bilaal (may Allah be pleased with him), at the time of Fajr prayer: “O Bilaal, tell me of a deed that you did in Islam, for which you most hope to earn reward, for I heard the sound of your sandals in front of me in Paradise.” Bilaal said: I have not done any deed in Islam for which I hope to earn reward more than the fact that I do not purify myself fully at some time of the night or day, but I pray as much as Allah wills I should pray with that purification.
At-Tirmidhi (3689) narrated that Bilaal (may Allah be pleased with him) said: I never gave the adhaan but I prayed two rak‘ahs, and I never invalidated my wudoo’ but I did wudoo’ immediately and thought that I owed it to Allah to pray two rak‘ahs.
Classed as saheeh by Shaykh al-Albaani (may Allah have mercy on him) in Saheeh Sunan at-Tirmidhi.
The hadith of Bilaal (may Allah be pleased with him) indicates that it is mustahabb to persist in doing wudoo’, and that it is mustahabb to offer a prayer immediately after doing wudoo’.
There is nothing in the hadith to indicate that it is mustahabb to do wudoo’ for every naafil prayer.
An-Nawawi (may Allah have mercy on him) said:
This indicates that it is mustahabb to pray following wudoo’, that doing so is Sunnah and that it is permissible to do so at times when offering (unspecified naafil) prayers is disallowed: at sunrise, when the sun is at its zenith, at sunset, and after Fajr and ‘Asr prayers, because it is a naafil prayer that is done for a specific reason. This is our view.
End quote from Sharh Muslim by an-Nawawi (8/13).
Ibn Hajar (may Allah have mercy on him) said:
This hadith indicates that it is mustahabb to keep oneself in a state of purity.
End quote from Fath al-Baari (3/35).
The scholars (may Allah have mercy on them) stated: Renewing wudoo’ is only mustahabb for one who prayed after doing the first wudoo’.
An-Nawawi (may Allah have mercy on him) said:
Our companions are unanimously agreed that it is mustahabb to renew wudoo’, which is when a person had wudoo’, then does wudoo’ again without having invalidated his wudoo’.
When is it mustahabb? There are five views concerning that, the soundest of which is if he offered a prayer, obligatory or naafil, with the first wudoo’ (then it is mustahabb to do wudoo’ for another prayer).
End quote from al-Majmoo‘ (1/495)
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said in Majmoo‘ al-Fataawa (21/376):
Rather the fuqaha’ discussion has to do with the one who prayed with the first wudoo’: is it mustahabb for him to renew his wudoo’?
With regard to one who did not pray with the first wudoo’, it is not mustahabb for him to renew wudoo’. Rather renewing wudoo’ in this case is a bid‘ah (innovation) and is contrary to the Sunnah of the Messenger of Allah (blessings and peace of Allah be upon him) and the way of the Muslims both during his lifetime and after his death, until the present time. End quote.
An exception is made to it being mustahabb to renew wudoo’ if one of the two prayers was connected to the other, such as the regular Sunnah prayers that are connected to obligatory prayers, or Taraweeh followed by Witr, or if the two prayers are put together, as in the case of one who puts Maghrib and ‘Isha’ together. In such cases it is not mustahabb to renew wudoo’, because there is no report of the Prophet (blessings and peace of Allah be upon him) doing that.
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said:
It is proven via mutawaatir reports that on the day of ‘Arafah the Prophet (blessings and peace of Allah be upon him) led the Muslims in praying Zuhr and ‘Asr, putting the two prayers together, and thousands prayed behind him whose numbers are known only to Allah. When he said the tasleem at the end of Zuhr, he led them in praying ‘Asr; neither he nor anyone else repeated his wudoo’, nor did he instruct anyone to repeat his wudoo’, and no one transmitted any report to that effect. This indicates that renewing wudoo’ is not mustahabb in all cases.
Sometimes he would offer an obligatory prayer and then a naafil prayer, and sometimes he would offer a naafil prayer and then an obligatory prayer, and sometimes he would offer an obligatory prayer then another obligatory prayer, all of that with one wudoo’.
Similarly, the Muslims would pray behind him at night in Ramadan with one wudoo’, on numerous occasions.
The Muslims at his time would do wudoo’, then they would pray so long as they did not invalidate their wudoo’, as is mentioned in the saheeh hadiths. There is no report from him – either with a saheeh or da‘eef isnaad – to indicate that he instructed them to do wudoo’ for every prayer. Saying that it is mustahabb to do so requires proof.
End quote from Majmoo‘ al-Fataawa (21/371-372)
And Allah knows best.