Abu Ghalib reported,

When the heads of the Azariqa were brought and mounted on the steps of Damascus, Abu Umama came. When he saw them, his eyes welled up with tears, and he said three times, "Dogs of the Fire. These are the worst of the slain ever killed beneath the canopy of the sky, and the best of the slain killed beneath the canopy of the sky are those whom these men killed."I asked, "What is the matter with you? Your eyes have welled up with tears."He replied, "Out of compassion for them, for they were once among the people of Islam."We said, "Is this from your own opinion, that these are dogs of the Fire, or is it something you heard from the Messenger of Allah ﷺ?"He said, "Would I be so bold? Rather, I heard it from the Messenger of Allah ﷺ not once, not twice, not three times." And he counted several times over.

عن أبي غالب يقول

لما أتي برؤوس الأزارقة، فنصبت على درج دمشق، جاء أبو أمامة، فلما رآهم دمعت عيناه، فقال: كلاب النار، ثلاث مرات، هؤلاء شر قتلى قتلوا تحت أديم السماء، وخير قتلى قتلوا تحت أديم السماء الذين قتلهم هؤلاء، قال: فقلت: فما شأنك؟ دمعت عيناك، قال: رحمة لهم، إنهم كانوا من أهل الإسلام، قال: قلنا: أبرأيك؟ قلت: هؤلاء كلاب النار أو شيء سمعته من رسول الله ﷺ؟ قال: إني لجريء، بل سمعته من رسول الله ﷺ غير مرة ولا ثنتين ولا ثلاث. قال: فعد مرارا.