Using used water for wiping the head in ablution
14-1-2023 | IslamWeb
Question:
Assalaamu 'Alaykum. Fatwa 177311 is about using new water for wiping the head in wudhu. I don't use new water and just use the leftover water from washing my arms. Is the position regarding the permissibility of not using new water strong enough, or should i make up past prayers? If I don't use new water, can i wipe the ears without new water or would that be wiping with water used from wiping, and fatwa 177311 states "...the water remaining after wiping is not permissible to use again"? If i can't, should i make up the prayers in the past as I've done this?
Answer:
All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad 
is His slave and Messenger.
Scholars held different opinions regarding the ritual purity (and the reuse) of the used water (for ritual purification). The opinion of the majority of scholars is that it is ritually pure, but cannot be used for ritual purification. Accordingly, if you wipe your head with the used water that remained in your hand after the obligatory washing of the arms, wiping your head is not valid according to the opinion of the majority of scholars.
If you were washing your arm for the second or third time during the ablution, the used water that remained in your hand is ritually pure and may be used for ritual purification; wiping your head with it would be valid.
As for the ears, the act of Sunnah is to wipe them with the water used to wash the head because the ears are part of the head. Scholars held different opinions in this regard, and what we have mentioned is closer to the Sunnah, Allah Willing, and this was the opinion chosen by Ibn Taymiyyah 
.
As for the past prayers, you do not have to make up for any of them, Allah willing. As long as your prayer is valid according to a group of scholars, i.e., those who believed that the used water is ritually pure and may be used for ritual purification, there is nothing wrong with you adopting this opinion. This is because some scholars allowed acting upon the outweighed opinion after the performance of the action and the difficulty of redressing it when some scholars held a less stringent view on the matter.
The opinion that the used water is ritually pure and may be used for ritual purification, even if it is contrary to that of the majority of scholars and the more prudent view in this regard, it is still a strong and considerable opinion. There is nothing wrong with adopting it with regard to what you had done in the past.
Allah knows best.