What does moral cleanliness mean?

In the Qur’an Allah states that people should be morally clean too. It is stated that he who avoids the evil of his soul (nafs) and purifies it will succeed. Allah states in Surat ash-Shams:

By the soul and the One Who proportioned and inspired it with knowledge of depravity and with its sense of duty, he who purifies it has succeeded, he who covers it up has failed. (Surat ash-Shams, 7-10)

Moral purity is attainable, as we are informed in the verse, when one avoids the evil that one’s soul commands one to commit. Someone who is morally pure has a sincere faith and a peaceful spirit. All his thoughts and all his deeds are righteous. In every event he encounters, he behaves in a manner that shows that he is well pleased with Allah. He is sincere and genuine. He well knows that there is definitely goodness in everything Allah creates. Such people are purified from the corruption in their soul. Allah heralds the good end that these people will meet:

… You can only warn those who fear their Lord in the Unseen and establish prayer. Whoever is purified, is purified for himself alone. Allah is your final destination. (Surah Fatir, 18)

He who has purified himself will have success. (Surat al-A’la, 14)

What does moral cleanliness mean?