Is it true that a Muslim forsaking his brother for more than three nights prevents the acceptance of good deeds? And what are the consequences of that?

It is not permissible for a Muslim to shun his brother for more than three nights, except for a legitimate Shar'i (Islamic legal) excuse such as open transgression (fisq) or innovation (bid'ah). The estrangement is removed by offering salutations (salam). Shunning does not prevent the recording of good deeds, but it deprives one of Allah's forgiveness due to animosity. A person is not held accountable for committing unlawful acts before puberty. Puberty for a male is reached by nocturnal emission, the growth of pubic hair, or reaching 15 years of age. For a female, it is marked by menstruation or pregnancy.