Assalamualaikum ustaz. Is capybara (also known as water swine) ruled as najis just like the swine found on land? 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.
Basically, dogs and swine are categorized as mughallazah najis (major najis) and it is obligatory to be washed according to the methodology set by syarak. This is as stated by Allah SWT:
حُرِّمَتْ عَلَيْكُمُ الْمَيْتَةُ وَالدَّمُ وَلَحْمُ الْخِنزِيرِ
“Prohibited to you are dead animals, blood, the flesh of swine,” 
Dr Wahbah al-Zuhaili stated that the prohibition of swine includes all of its body parts including its fat and skin. As for the specific statement of only its flesh is because it serves the most important purpose, which is to be eaten. Indeed, syarak prohibits benefitting from all parts of swine according to the statement of Allah SWT:
أَوْ لَحْمَ خِنزِيرٍ فَإِنَّهُ رِجْسٌ
“Or the flesh of swine – for indeed, it is impure,” 
Likewise, Rasullullah PBUH said:
مَن لَعِبَ بالنَّرْدَشِيرِ، فَكَأنَّما صَبَغَ يَدَهُ في لَحْمِ خِنْزِيرٍ ودَمِهِ
“He who plays backgammon is as though he had dipped his hand in a pig’s flesh and blood.” 
Thus, touching – which means holding – is prohibited, hence, eating it is also prohibited. 
What is water swine?
Previous scholars discussed the rulings of capybara (خِنْزِيرُ الْمَاءِ) in their books. However, a question arises, is the discussed animal, water swine the same as the capybara known today? Kamaluddin al-Damiri cited in his book that Malik was once asked regarding water swine and he answered:
أنتم تسمونه خنزيرا يعني أن العرب لا تسميه بذلك لأنها لا تعرف في البحر خنزيرا والمشهور أنه الدلفين
“You’ve named it as water swine while the Arabs didn’t name it as such, for it isn’t known that there is swine in the sea and it is famously known as dolphins.” 
This statement is strengthened or supported when Dr Muhammad al-Zuhaili included water swine as an aquatic animal that isn’t similar to normal fish and stated that it is halal and doesn’t require slaughtering just like other fishes. 
Thus, if the water swine meant by previous scholars is dolphins, then there isn’t any issue in touching or holding it, for it is included as a halal and pure marine animal. For further explanation regarding this matter, you can refer to our previous article titled: #320 Eating Dolphins. 
Capybara is different from swine that we know
However, if water swine meant is the animal known as capybara now, then we should first consider whether capybara is an animal that originates from the same family and species as swine – as we commonly know them – or not?
Capybara or its scientific name Hydrochoerus hydrochaeris is the largest rodent of all rodents. It looks like a little pig or a big guinea pig. It can swim well. Some people call it a water pig.  Capybara is the only species of the Hydrochoeridae family. It looks similar to the cavy and guinea pig of the Caviidae family. 
While swine (pigs), whether wild or domestic, are omnivorous mammals from the Suidae family. It has a heavy body, short legs, and thick skin covered with thin feathers. 
Thus, it is clear that capybara is not descended from the same species and family as swine – which we are familiar with. This is because it comes from the Hydrochoeridae family while swine are from the Suidae family.
The ruling of touching capybara
The origin of every animal is pure – which means it is not najis – unless there isn’t any evidence showing otherwise such as the najis status of swine, dogs or others. Al-Khatib al-Syirbini stated that every animal – that is alive – is pure except what has been exempted by syarak.  Thus, the capybara is included as pure animal and its carcass is categorized as moderate najis.
Furthermore, there isn’t any specific evidence that states capybara or water swine as najis as swine that we usually know. Moreover, water swine’s origin is not from the same family as the swine that we know. However, it originates from the family Hydrochoeridae and is similar to the family Caviidae.
Just by calling it swine doesn’t affect its rulings for an Islamic legal maxim state:
العِبْرَةُ بِحَقَائِقِ الأَشْيَاءِ لاَ بِأَسْمَائِهَا
“The ruling of something is considered based on the reality and not on its name.”
Furthermore, al-Mawardi rejected their argument on the prohibition of water swine just by comparing it with normal swine found on land.  He said the difference in the habitat although they have the same name and physical characteristics, they have their own ruling, for example, African wild ass and domesticated donkeys, both have the same name and similar physical characteristics. However, both have different rulings where wild donkeys are permissible to be eaten while domesticated donkeys are prohibited to be eaten, for both live in different habitats although both are land animals. Hence, any animal with different habitat, for example, one is a marine animal while the other is a land animal, assuredly have different rulings even if they share the same name and similar physical characteristics. 
Moreover, this matter is clearly stated by Ibn Rusyd al-Hafiz in his statement saying that Muslims have agreed that swine is prohibited. The word swine means any type of swine as long as it is swine and not just share the name or said as swine but in reality, it is not from the swine species, for instance, water swine. 
According to the above discussion and arguments, in our opinion, it is permissible to touch water swine or capybara because actually, it is not the same as swine found on land as we know it. Thus, it is categorized as pure animals and doesn’t follow the rulings of swine and their offspring. Its carcass is considered mutawassitah najis (moderate) and not mughallazah najis (major) like swine found on land.
May Allah SWT grant us all a clear understanding in religion. Amin.
 Surah al-Ma’idah: 3
 Surah al-An‘am: 145
 Narrated by Muslim (2260)
 See al-Tafsir al-Munir, 6/77
 See Hayah al-Hayawan al-Kubra, 2/429.
 See al-Mu‘tamad fi al-Fiqh al-Syafi‘i, 2/548.
 See Ensiklopedia Dunia, Terj. DBP, 5/95.
 See Encyclopedia Britannica, https://www.britannica.com/animal/capybara.
 See Encyclopedia Britannica, https://www.britannica.com/animal/pig-mammal-group.
 See Mughni al-Muhtaj, 1/226
 This is the same as the third opinion cited by al-Nawawi in his book considering other animals similar to it such as cows and goats, which are permissible to be eaten. If other similar animals are found and aren’t permissible to be eaten, then it is also prohibited to be eaten like water swine and seal. Next, if there isn’t any comparable animal on land, then it is permissible to be eaten. (See al-Majmu‘ Syarh al-Muhazzab, 9/34).
 See al-Hawi al-Kabir, 15/62.
 See Bidayah al-Mujtahid wa Nihayah al-Muqtasid, 1/10.