I sometimes feel hardness in my heart and something like inconspicuous Shirk (associating others with Allah in His Divinity or worship) or envy, what is the remedy for this?
Moreover, I used to invoke Allah with the Du'a' (supplication) that was said by the Prophet (peace be upon him):
O Allah, I seek refuge with You from associating anything with You knowingly, and I seek Your forgiveness for what I know not.
I make Du`a' to Allah also to grant forgiveness and mercy to those whom I envy in order to expiate my sins towards them. Is there any other remedy that cures this dangerous malady?
(Part No. 1; Page No. 276)
You have to observe a lot of Dhikr (Remembrance of Allah), recite the glorious Qur'an, do many supererogatory acts of `Ibadah (worship) and keep the company of righteous people. You also have to be sincere to Allah in doing acts of `Ibadah and avoid Riya' (showing-off) by doing righteous deeds for the sake of Allah Alone in order to be prosperous in the hereafter. As for getting rid of envy, you have to believe that all graces and favors are gifts from Allah (Glorified and Exalted be He) and that He is the One who divides them among His servants. Allah (Exalted be He) says:
It is We Who portion out between them their livelihood in this world, and We raised some of them above others in ranks, so that some may employ others in their work. But the Mercy (Paradise) of your Lord (O Muhammad صلى الله عليه و سلم) is better than the (wealth of this world) which they amass.
A person should love for others what they love for themselves. The Prophet (peace be upon him) says:
None of you will believe until he loves for his brother what he loves for himself.
People should keep themselves away from jealousy and envy by being busy with beneficial good sayings and acts.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.