Which are the best books on tenderizing hearts?

The best book for softening hearts is the Holy Qur'an, for it is an admonition, a healing, a guidance, and a mercy, and a Muslim should not turn away from it. A Muslim should frequently recite it with contemplation and humility, seeking assistance from concise exegeses such as Tafsir Al-Sa'di. In addition to the Qur'an, there are many books on softening hearts, including sections in hadith collections and independent books such as "Al-Bahr Al-Ra'iq fi Al-Zuhd wal-Raqa'iq" by Ahmed Farid, and "Al-Zuhd wal-Raqa'iq" by Ibn Al-Mubarak, and books by Ibn Al-Qayyim like "Madarij Al-Salikin," "Al-Jawab Al-Kafi," and "Tariq Al-Hijratayn," and "Lata'if Al-Ma'arif" by Ibn Rajab, and "Tazkiyat Al-Nafs" by Ibn Taymiyyah, and books about death and the Afterlife such as "Al-Tadhkirah fi Ahwal Al-Mawta" by Al-Qurtubi.