Is one who does not forgive his wife’s mother—who instigates disputes and does not desire reconciliation—sinful, given his feeling of resentment towards her, especially with the advent of the month of Ramadan?

The person with the greatest right over a man is his mother, and over a woman is her husband. A wife's kindness to her husband's mother is a good deed towards her husband. One should be keen to reconcile with the husband's mother, especially with the arrival of Ramadan, in accordance with His, the Almighty's, saying: "And those who restrain anger and pardon people," and His saying: "Repel evil with that which is best." Refusing to forgive is from the devil's deception to cause one to miss out on a great reward, as per His, the Almighty's, saying: "So whoever pardons and makes reconciliation - his reward is due from Allah," and the Prophet's (peace be upon him) saying: "It is not lawful for a Muslim to abandon his brother for more than three [days], and the better of them is the one who initiates the greeting."