The Quran

وَلَقَد مَكَّنّاهُم فيما إِن مَكَّنّاكُم فيهِ وَجَعَلنا لَهُم سَمعًا وَأَبصارًا وَأَفئِدَةً فَما أَغنىٰ عَنهُم سَمعُهُم وَلا أَبصارُهُم وَلا أَفئِدَتُهُم مِن شَيءٍ إِذ كانوا يَجحَدونَ بِآياتِ اللَّهِ وَحاقَ بِهِم ما كانوا بِهِ يَستَهزِئونَ

Muhammad Asad

And yet, We had established them securely in a manner in which We have never established you, [people of later times;]¹ and We had endowed them with hearing, and sight, and [knowledgeable] hearts:²but neither their hearing, nor their sight, nor their hearts were of the least avail to them, seeing that theywent on rejecting God's messages; and [in the end] they were overwhelmed³ by the very thing whichthey had been wont to deride.

This relates in the first instance to the pagan contemporaries of the Prophet, but applies to later generations as well. - The tribe of 'Ad were the unchallenged lords in the vast region in which they lived (cf. 89:8 - "the like of whom has never been reared in all the land"). Moreover, the social conditions of their time were so simple and so free of the many uncertainties and dangers which beset people of higher civilizations that they could be regarded as more "securely established" on earth than people of later, more complex times.
I.e., intellect and feeling, both of which are comprised in the noun fu'ad.
Lit., "enfolded".