Those who are infidels aid one another. Unless you do the same there will be discord in the land and anarchy.
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Tafseer
'Abdullāh Ibn 'Abbās / Muḥammad al-Fīrūzabādī
تفسير : (and those who disbelieve are protectors one of another-) in the matter of inheritance (if ye do not so) divide estate between relatives as has been explained to you, (there will be confusion in the land) through idolatry and apostasy, (and great corruption) by means of killings and transgression.
Jalāl al-Dīn al-Maḥallī
تفسير : and those who disbelieve are allies of one another, in terms of [mutual] support and inheritance, and so there is no inheriting between you and them. unless you do this, [unless] you ally yourselves with the believers and sever relations with the disbelievers, there will be sedition in the land and great corruption, with disbelief gaining power and islam becoming weak.