When discussing the interpretation and rulings of shari'a on verse (5:96) in his tafssir imam al-Qurtobi quoted the known hadith saying:
"lts water is pure, and its dead creatures are halal."
(Sources: al-Muwatta' , sunan ibn Majah 1, 2, 3, 4, sunan abi Dawod, Jami' at-Tirmdihi, sunan an-Nasa'i 1, 2 and 3)
The same hadith was also quoted by ibn Kathir in his tafsir of verse (25:53):
(and that is salty and bitter;)
meaning that it is salty, bitter and not easy to swallow. This is like the seas that are known in the east and the west, the Atlantic Ocean and the Straits that lead to it, the Red Sea, the Arabian Sea, the Persian Gulf, the China Sea, the Indian Ocean, the Mediterranean Sea, the Black Sea and so on, all the seas that are stable and do not flow, but they swell and surge in the winter and when the winds are strong, and they have tides that ebb and flow. At the beginning of each month the tides ebb and flood, and when the month starts to wane they retreat until they go back to where they started. When the crescent of the following month appears, the tide begins to ebb again until the fourteenth of the month, then it decreases. Allah, may He be glorified, the One Whose power is absolute, has set these laws in motion, so all of these seas are stationary, and He has made their water salty lest the air turn putrid because of them and the whole earth turn rotten as a result, and lest the earth spoil because of the animals dying on it. Because its water is salty, its air is healthy and its dead are good (to eat), hence when the Messenger of Allah was asked whether sea water can be used for Wudu', he said:
(Its water is pure and its dead are lawful.)
This was recorded by Malik, Ash-Shafi`i and Ahmad, and by the scholars of Sunan with a good ﴿Jayyid﴾ chain of narration. (Source qtafsir)
This hadith declares the sea water as clean by default az-Zurqani in his commentary on al-Muwatta made clear that this water is considered as clean by itself and cleaning (the body).
While ibn 'Abd al-Barr considered this hadith as one which wouldn't be used as a clear proof by the people of knowledge as it is mursal after quoting that the narrator -appearing in imam Malik's narrator chain- al-Mughira ibn abi Burdah is rather unknown or has only one single known Student according to some scholars and quoting a much sounder chain in his al-Istidhkar he also referred to his own statements in at-Tamheed (note that an-Nasa'i is the most prominent hadith scholar who considered him as trustworthy). He also pointed at the fact that even if this hadith doesn't appear in the two sahihs it is accepted by all hadith scholars as a given rule.
Ibn 'Abd al-Barr further quoted that there are statements of ibn 'Omar and Abdullahn ibn 'Amr ibn al-'Aas on the undesirability of sea water (scholars commented this saying they considered it frowned upon to use it themselves not haram). And concluded saying (My own translation take it carefully):
1572 - وليس في أحد حجة مع خلاف السنة .
There's no proof by anyone if it is opposing the -clear- sunnah.
He then quoted a tafssir attributed to ibn 'Abbas (25:53) (My own translation again):
1573 - وقد روى قتادة عن موسى بن سلمة الهذلي قال : سألت ابن عباس عن الوضوء بماء البحر ، فقال : هما البحران يريد قول الله تعالى : هذا عذب فرات وهذا ملح أجاج [ الفرقان : 53 ] لا تبال بأيهما توضأت .
It was narrated by Qatadah from Musa ibn Salamh al-Hudahli who said: I asked ibn 'Abbas about the wudu' from sea water and he answered: these are the two seas meant by "this is palatable and sweet, and that is salty and bitter" don't care about any of them you use for wudu'.
Then he quoted a consensus (note that the consensus of ibn 'Abd al-Barr is to be taken carefully sometimes) (My own translation):
1573 - وهذا إجماع من علماء الأمصار الذين تدور عليهم وعلى أتباعهم الفتوى . وكذلك عندهم كل ماء مستبحر كثير غير متغير بما يقع فيه من الأنجاس .
And this is a consensus among the scholars of the lands to whom and whom's students the practice of giving fatwa is known and the same applies to each water which is close to sea and in a large amount which is larger than that of the najis things in it.
Fiqh view on water
Water in fiqh can be:
- tahur: it is both ritually pure and can be used to remove impurity.
- tahir: is ritually pure but not tahur (can't be used for worsphip matters like wudu' and ghusl, but for cleaning or drinking for example)
- contamined with impurity.
Tahur is defined as the water that come down from the sky or welld up from earth and none of whose three fundamental properties -namely. its color taste and smell- have been altered by any those things which cause water to cease being tahur. Nor may such water have been used before (with difference in opinion see Is it permissible to re-use the water that has been already used [by myself] for ablution?). (All this can be found in al-Jaziri's Islamic Jurisprudence according to the four sunni schools p. 36 ff)
So from a fiqh perspective water can only be doubtful if a change has altered or changed it else it is considered as clean.
From this we may conclude that the statement of ibn 'Abd al-Barr is correct and that sea water by default is tahur and therefore permissible for the use for ablution.
