Musnad Abu Ya'la al-Mawsili 155:143

Nuḥ ibn Ḥātim al-Baghdādī narrated to us, Hishīm narrated to us, from al-Zuhrī, from Abū Salamah, from Abū Hurayrah, who said: ‘Uyaynah ibn Ḥiṣn entered upon the Messenger of Allah (may Allah bless him and grant him peace), and he saw him kissing al-Ḥasan and al-Ḥusayn. He said, “Do you kiss them, O Messenger of Allah?” ‘Uyaynah said, “I have ten [children], and I have not kissed any one of them.” The Messenger of Allah (may Allah bless him and grant him peace) said, “He who does not show mercy will not be shown mercy.”