[Pooya/Ali Commentary 56:39] (see commentary for verse 7)

1. Of sins, association in any form even ungratefulness, is unforgivable, unless undone under penance and reversion to God. 2. Of sins involved in swallowing rights of others, one cannot absolve oneself, unless the creditor forgives him. 3. Sins causing wrong to self (as belief in God and His creatures) are subject to forgiveness, under penance to God.