Justice Amir Ali in his famous work the Spirit of Islam...

Justice Amir Ali in his famous work the Spirit of Islam, quotes Osborn in depicting the personality of Ma'aviah:- "Astute, unscrupulons and pitiless, says Osborn the first Kalif of the Omayyids (Ma'aviah) shrank from no crime necessary to secure his position. Murder was his accustomed mode of removing a formidable opponent. The grandson of the Prophet he caused to be poisoned. Malek- al- Ashtar, the heroic lieutenant of Ali, was destroyed in the like way.

To secure the succession of Yazeed, Ma'aviah hesitated not to break the word he had pledged."