Is it true that Ibn Al-Qayyim said: "To the extent of your eagerness to reform people's hearts, Allah will reform your heart," and what is its evidence from the Qur'an and Sunnah?

It has not been proven that the statement is from the words of Ibn al-Qayyim, but its meaning is correct: that recompense is of the same kind as the deed. So, whoever strives to reform people's hearts, Allah will reform his heart. This is supported by the hadith: "Three things that the heart of a Muslim will never be envious about: Sincerity in deeds for the sake of Allah, advising the Muslim leaders, and adhering to their community." And his (peace be upon him) saying: "There is no Muslim servant who supplicates for his brother in his absence, but the angel says: 'And for you the like of it.'"