As-Salaam alaikum,
The Noble Apostle of Allah, Sallallahu alaihi Wasallam, said:--

"Renew your faith!" His blessed companions asked, "How do we renew our faith, O Messenger of Allah"?
He said: "Say LA ILAHA ILLALLAH in abundance. The utterance of it allows no sin to remain, no
other deeds resembles it, and no evil comes between it and Allah; and it reaches the Divine Court."

Sheikh Abd al-Khaliq al-Shabrawi (1887-1947) in
his book: ''The Degrees of the Soul.''