The Quran

102

وَآخَرونَ اعتَرَفوا بِذُنوبِهِم خَلَطوا عَمَلًا صالِحًا وَآخَرَ سَيِّئًا عَسَى اللَّهُ أَن يَتوبَ عَلَيهِم ۚ إِنَّ اللَّهَ غَفورٌ رَحيمٌ

Muhammad Asad

And [there are] others¹ - [people who] have become conscious of their sinning after having done righteous deeds side by side with evil ones;² [and] it may well be that God will accept their repentance: for, verily, God is much-forgiving, a dispenser of grace.

I.e., neither believers in the full sense of the word nor hypocrites, but half-hearted, confused waverers between right and wrong, or between truth and falsehood.
Lit., "who have acknowledged their sins [after] having mingled a righteous deed with another that was evil". Although it relates primarily to the vacillating Muslims who refused to participate in the expedition to Tabuk, this verse alludes, in its wider meaning, to all sinners who - without external prompting - become conscious of their wrongdoing and repent of it.