Hawzah News Agency – The merciful prophet of Islam, peace be upon him and his household says:

إنَّ للَّهِ تعالى‏ في الأرضِ أوانِيَ، ألا وهِي القُلوبُ، فَأحَبُّها إلَى اللَّهِ، أرَقُّها وأصفاها وأصلَبُها؛ أرقُّها للإخوانِ، وأصفاها مِن الذُّنوبِ، وأصلَبُها في ذاتِ اللَّهِ.

'Allah, most High, has receptacles on the earth, and verily they are the hearts. The most beloved of hearts to Allah are the softest ones, the purest ones, and the firmest ones: those that are the softest to their brothers, those that are the most pure from sins, and those that are the firmest in the path of Allah.'

Source: Kanz al-Ummal, no. 1225