Musnad Ahmad 509:14

'Affan narrated to us, Wuhayb narrated to us, 'Abdullah ibn 'Uthman ibn Khuthaym narrated to us, from Sa'id ibn Abi Rashid, from Ya'la al-'Amiri: That al-Hasan and al-Husayn came racing toward the Messenger of Allah (may Allah bless him and grant him peace), so he embraced them both and said: "Indeed, children are a cause of stinginess and a cause of cowardice, and the last footprint that the Most Merciful stepped with was in Wajj."