Does quarreling—meaning shunning someone and not speaking to them, whether they are a disbeliever or a believer—prevent the forgiveness of sins for one who seeks forgiveness, and does it prevent the acceptance of good deeds?

Enmity towards non-Muslims does not prevent forgiveness. Rather, enmity towards polytheists for the sake of Allah and abandoning affection for them is among the firmest bonds of faith. Allah Almighty says: "You will not find a people who believe in Allah and the Last Day loving those who oppose Allah and His Messenger, even if they were their fathers or their sons or their brothers or their kindred." As for animosity and enmity towards Muslims without a religious reason, it is reprehensible and it is feared that it may be a barrier to the forgiveness of sins and the acceptance of good deeds. The Prophet, peace and blessings be upon him, said: "Three whose prayer does not rise a handspan above their heads: a man who leads a people in prayer while they dislike him, a woman who spends the night while her husband is angry with her, and two brothers who have severed ties with each other." Therefore, one must repent from animosity in the hope of attaining Allah's forgiveness.