Is the heart's attachment to someone other than the husband—after marriage and having children—considered marital infidelity, and what should be done about it?

Sincere repentance from the forbidden relationship is obligatory, along with seeking refuge in Allah to remove the attachment. One should dedicate oneself to reciting and contemplating the Quran, observing the obligatory prayers, and performing many supererogatory acts of worship. It is necessary to sever all ties that remind one of that man, and when he comes to mind, one must seek Allah's forgiveness and refuge in Him. Filling the heart with the love of Allah and sincerity to Him removes attachment to others. If the attachment becomes overwhelming but is resisted without committing any forbidden act, there is no punishment for it and it is not considered a betrayal of the husband. Whoever is afflicted with عشْق (passionate love) and remains chaste and patient, will be rewarded for their piety.