What does it mean to persist in a sin?
And those who, when they commit an immorality or wrong themselves [by transgression], remember Allah and seek forgiveness for their sins - and who can forgive sins except Allah ? - and [who] do not persist in what they have done while they know.
Qur'aan 3:135
The Messenger of Allaah (sallallaahu alayhi wa sallam) said:
Indeed, a slave (of Allaah) commits a sin, and then says O my Lord, I have sinned so forgive me. Thereupon his Lord says: My slave knows that he has a Lord who forgives sin and punishes for it (i.e. sin). I have forgiven My slave.Then, he remains (without committing a sin) so long as Allaah Wills.
Then, he falls into (or commits) a sin.
Thereupon he says: I have committed - or fallen into- another (sin), so forgive me. Thereupon his Lord says: My slave knows that he has a Lord who forgives sin and punishes for it (i.e. sin). I have forgiven My slave.Then, he remains (without committing a sin) so long as Allaah Wills.
Then, he falls into (or commits) a sin (for the) third (time).
Thereupon he says: I have committed - or fallen into- another (sin), so forgive me. Thereupon his Lord says: My slave knows that he has a Lord who forgives sin and punishes for it (i.e. sin). I have forgiven My slave, so let him do what he likes.
Sahiih al-Bukhaari Hadiith No. 7507
The scholars of Tafsiir have three views in regards to what persisting in sin means.
The first view is that it means that one does not continue to do the sin and does not remain steadfast on it. Rather, one repents and asks forgiveness for the sin one commits. This is the view of Qataadah.
The second view is that when has an interest to commit a sin he does not do so. He does not fall into the sin.
The third view is that one does not repent from the sin one commits.
Imaam al-Tabari holds the view that the most correct view in the matter is that to persist in a sin means to continue to do the sin and not repent from it and to not ask forgiveness.
He says that the view that it means that one should not commit the sin when one is incited to do so does not make sense. The Verse says the ones who sin and then ask for forgiveness. If persistence had meant never to sin to begin with, when one is incited to do so, then asking for forgiveness would have no meaning to it.
Reference(s):
زاد المسير في علم التفسير
Volume 1 Page 225
Tafsir al-Tabari