Crab, one of the animals that people thought live in two worlds is a kind of aquatic animal, because it
breathes with gills, live in the water, and will never release eggs on land, but in the water; since it requires oxygen from the water.
There are four types of mangrove crabs that are frequently consumed and become a commodity, namely: Scylla serrata, Scylla tranqueberrica, Scylla olivacea and Scylla pararnarnosain. The four types of mangrove crabs are by the general public simply called crabs.
Crabs, including the four types above, only live in fresh water, in sea water, or live in both the sea and fresh water. So there is no crab living in two worlds (sea and land).
Crabs are halal to be consumed, except the poisonous one. However, most types of crabs are not toxic. Frogs, which coincidentally live in two worlds, are prohibited, based on Hadith.
From Abdurrahman bin Uthman al-Qurasyis-yi that a physician asked to prophet Muhammad pbuh about frog that he mix it in a drug, the Prophet forbade to kill it (narrated by Ahmad and approved by Hakim and also narrated by Abu Dawud and Nasa’i).
That is probably why some people think that animals that live in two worlds are disallowed. There is no source (from either the Quran or hadith) which forbids animal that live in two worlds to be consumed.
As mentioned in the Al Qur’anul kariem (QS Al Maidah: 3),
Prohibited to you are dead animals, blood, the flesh of swine, and that which has been dedicated to other than Allah, and (those animals) killed by strangling or by a violent blow or by a head-long fall or by the goring of horns, and those from which a wild animal has eaten, except what you (are able to) slaughter (before its death), and those which are sacrificed on stone altars, and (prohibited id) that you seek decision through divining arrows.
In the book of Ibn Rushd Bidayatul Mujtahid is stated that Imam Syafii forbids turtles and crocodiles on the basis of its repulsive (khabaits), not because they live in two worlds. It is based on the Quran surah Al-A’raf verse 157,
Those who follow the Messenger, the unlettered prophet, whom they find written [i.e. mentioned] in what they have of the Torah and the Gospel, who enjoins upon them what is right and forbids them what is wrong and makes lawful for them the good things and prohibits for them the evil and relieves them of their burden and the shackles which were upon them. So they, who have believed in him honoured him, supported him and followed the light which was sent down with him – it is those who will be successful.
According to the rule of origin, all foods are halal except those prohibited in the Kitab (Qur’an and Hadith). We could not simply forbid animals that live in two worlds.
Wallahu a’lam
