Assalamualaikum ustaz. What is the ruling of performing ablution but being wasteful with the water? Hope for an explanation.
Waalaikumussalam wrt. wbt.,
Alhamdulillah, praise and gratitude to Allah SWT for His countless blessings for us all. Praise and salutations to our beloved Prophet Muhammad PBUH, his family, companions, and all those who follow his footsteps until the Final day.
We start with the statement of Allah SWT:
إِنَّ الْمُبَذِّرِينَ كَانُوا إِخْوَانَ الشَّيَاطِينِ ۖ وَكَانَ الشَّيْطَانُ لِرَبِّهِ كَفُورًا
“Indeed, the wasteful are brothers of the devils, and ever has Satan been to his Lord ungrateful.” 
This verse shows that being excessive in spending one’s property – and other matters that lead to wastefulness – is a part of the temptation of the shaytan. Thus, if a person is being wasteful, in truth he is obeying and following the shaytan. 
Definition of wasteful
Wasteful is defined as being excessive that it is then wasted or thrown away.  There are some scholars who differentiate the meanings of israf (excessive) and wasteful, where israf refers to the usage of something that is necessary excessively more than necessary. While wasteful refers to the usage of using or utilizing something unnecessary. 
Performing ablution but being wasteful with the water
Regarding this matter, the author of al-Fiqh al-Manhaji stated that the usage of excessive water or being wasteful with water is included as makruh matters when performing ablution.  Furthermore, it is cited in al-Mausu‘ah al-Fiqhiyyah, that scholars have agreed that excessive usage of water is makruh.  Allah SWT states:
وَلَا تُسْرِفُوا ۚ إِنَّهُ لَا يُحِبُّ الْمُسْرِفِينَ
“But be not excessive. Indeed, He likes not those who commit excess.” 
Excessive means transgressing the normal modest limit.  In another hadith, Rasullullah PBUH said:
إِنَّهُ سَيَكُونُ فِى هَذِهِ الأُمَّةِ قَوْمٌ يَعْتَدُونَ فِى الطَّهُورِ وَالدُّعَاءِ
“In this community there will be some people who will exceed the limits in purification as well as in supplication.” 
Furthermore, there is a narration from Abdullah bin ‘Amr R.Anhuma where Rasullullah PBUH went past a place and he saw Sa’d was performing ablution. The Prophet PBUH stopped and said:
مَا هَذَا السَّرَفُ. فَقَالَ: أَفِي الْوُضُوءِ إِسْرَافٌ؟ قَالَ: نَعَمْ وَإِنْ كُنْتَ عَلَى نَهَرٍ جَارٍ
“’What is this extravagance?’ He said: ‘Can there be any extravagance in ablution?’ He said: ‘Yes, even if you are on the bank of a flowing river.'” 
This shows that the act of being excessive when using water while performing ablution is restricted by Rasullullah PBUH, even when there is a lot amount of water available such as when one is at sea, by the river or others.
Syeikh Mulla Ali al-Qari stated that being excessive when performing ablution whether it is by adding more than three times of washing or additional or extra water when using water. Abdullah bin ‘Amr asked whether there is such a thing as being excessive when performing ablution – or being wasteful – according to what has been previously stated, ‘there is nothing good out of being excessive or wasteful in doing good deeds.’ Hence, he assumed there that there excessive doesn’t exist in matters of obedience and worship. Thus, the Prophet PBUH corrected his assumption and said: ‘Yes, even if you are on the bank of a flowing river.’ The reason is in this matter, there is wastefulness in utilizing one’s time of his age, or transgressing the syar’i limit in ablution as previously stated. 
According to the above discussion, we concluded that being excessive in the usage of water when performing ablution is makruh. According to the prophetic guidance of the Prophet PBUH, where the Prophet PBUH perform ablution with just one mudd of water. This is as narrated from Ibn Jabr, where he heard from Anas RA, he said:
كَانَ النَّبِيُّ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ يَغْسِلُ، أَوْ كَانَ يَغْتَسِلُ، بِالصَّاعِ إِلَى خَمْسَةِ أَمْدَادٍ، وَيَتَوَضَّأُ بِالمُدِّ
“The Prophet used to perform ablution with a mudd of water and wash with a sa‘ up to five mudds.” 
The reason is the attitude of being excessive is not from the values of Islam, moreover, it doesn’t reflect the character of a Muslim who is someone who is modest in every situation.
May Allah SWT grant us all a clear understanding in practising this religion. Amin.
 Surah al-Isra’: 27
 See Zubdah al-Tafasir min Fath al-Qadir, pg. 368.
 See al-Ta‘rifat oleh al-Jurjani, pg. 24.
 See al-Fiqh al-Manhaji, 1/60.
 See al-Mausu‘ah al-Fiqhiyyah, 4/180.
 Surah al-A‘raf: 31
 See al-Fiqh al-Manhaji, 1/60.
 Narrated by Abu Daud (96)
 Narrated by Ibn Majah (425)
 See Mirqah al-Mafatih, 2/420-421.
 Narrated by al-Bukhari (201); Muslim (325)