Hawzah News Agency – Imam al-Baqir peace be upon him says:

تَعَرَّضْ لِرِقَّةِ القَلبِ بكَثرَةِ الذِّكرِ في‏ الخَلَواتِ.

'Embark upon softening the heart through constant remembrance [of Allah] in places of seclusion.'

Source: Tuhaf al-Uqul, p. 285