Shaykh al-Islām Ahmad ibn Taymiyyah—may Allah have mercy on him—also said:

Section: Purifying the Soul, and How It Is Purified by Refraining from Prohibited Acts While Performing Commanded Acts

Allah Most High says:

“Successful indeed is the one who purifies it,”

and:

“Successful indeed is the one who purifies himself.”

Qatādah, Ibn ʿUyaynah, and others said: “Successful indeed is the one who purifies his soul through obedience to Allah and righteous deeds.”

Al-Farrāʾ and al-Zajjāj said: “Successful indeed is a soul that Allah has purified, and failed indeed is a soul that Allah has debased.” Al-Wālibī likewise related this from Ibn ʿAbbās, but its chain of transmission is disconnected. This, however, is not what the verse means (1). Rather, the first interpretation is unquestionably what is intended, both in wording and meaning.

As for the wording, in His statement, “whoever purifies it,” “whoever” is a relative pronoun, and there must be a pronoun referring back