Abu Dharr reported: The Messenger of Allah, peace and blessings be upon him, said:

الْغِنَى فِي الْقَلْبِ وَالْفَقْرُ فِي الْقَلْبِ مَنْ كَانَ الْغِنَى فِي قَلْبِهِ لا يَضُرُّهُ مَا لَقِيَ مِنَ الدُّنْيَا وَمَنْ كَانَ الْفَقْرُ فِي قَلْبِهِ فَلا يُغْنِيهِ مَا أَكْثَرَ لَهُ فِي الدُّنْيَا وَإِنَّمَا يَضُرُّ نَفْسَهُ شُحُّها

Wealth is in the heart and poverty is in the heart. Whoever is wealthy in his heart will not be harmed no matter what happens in the world. Whoever is impoverished in his heart will not be satisfied no matter how much he has in the world. Verily, he will only be harmed by the greed of his own soul.

Source: al-Mu’jam al-Kabīr 1618, Grade: Sahih