نُكَفِّرْ عَنْكُمْ سَيِّئَاتِكُمْ
We shall remove your misdeeds from you.
Expiation may signify removal of the burden or consequence of a sin. The interpretive issue is whether this conveys automatic pardon of every minor sin or a particular promise under the relevant conditions.
Reports on the expiatory effect of prayer and other worship sometimes include the condition of avoiding major sins. This supports the benefit of worship, but it does not collapse every moral, legal, and interpersonal consequence into one unrestricted cancellation.