Hazrat Shaikh Moulana Muhammad Zakariyya (rahmatullahi ‘alaih) once mentioned:
If a person is swearing you and speaking ill of you behind your back, he is actually giving you his good deeds. If he does not have sufficient good deeds to give you, then he is taking your evil deeds onto his own head. A hadeeth has also mentioned, “Whoever swears or hits someone, retribution will definitely be taken from him, to the extent that retribution will even be taken on behalf of the hornless goat (that was butted by a goat with horns).” (Suhbat Baa Awliyaa pg. 94)
Source: Ihyaauddeen.co.za