“For that reason, We decreed for the Children of Israel that whoever kills a soul, unless in retribution for murder or for spreading corruption in the land, it is as though he has killed all mankind; and whoever saves a life, it is as though he has saved all mankind.”

And the angels said:

“Will You place in it someone who will spread corruption there and shed blood?”

The foundation of righteousness is monotheism and faith, while the foundation of corruption is associating partners with Allah and disbelief. As He said of the hypocrites:

“When they are told, ‘Do not spread corruption in the land,’ they say, ‘We are only reformers.’ Indeed, it is they who spread corruption, but they do not realize it.”

This is because the soundness of anything consists in its being such that its intended purpose is realized in it and through it. Thus, the jurists say: a valid contract is one that produces its legal effects and achieves its intended purpose; an invalid contract is one that neither produces its legal effects nor achieves an intended purpose. What they call ‘valid,’ as opposed to ‘invalid,’ is what is sound.

The early generations frequently used the expressions ‘This is not sound’ or ‘This is sound,’ just as later scholars frequently used ‘This is valid’ and ‘This is not valid.’

Allah Most High created man solely to worship Him, and his body follows his heart. As the Prophet, may Allah bless him and grant him peace, said in the authentic hadith:

“Indeed, there is a piece of flesh in the body: when it is sound, the rest of the body is sound, and when it is corrupt, the rest of the body is corrupt. Indeed, it is the heart.”

The heart’s soundness consists in the realization, in it and through it, of the purpose for which it was created, namely: