Imam al Qurtubi (Allah have mercy on him) said,

Understand it very clearly that following things soften the worst hardened hearts,
1. Visiting the graves
2. Listening to the discourses of pious scholars
3. Reading about the past obedient ascetics and scholars
4. Remembrance of that which will uproot all pleasures, ward off all desires, separate one from others, make existence detestable, and orphan the children who were adored by their parents. That is, death.’

Ebrat ka saman, page 27-8, Urdu translation of Imam Sha’rani (Allah have mercy on him)’s Mukhtaser Tazkirah al Qurtubi,