Musnad Ahmad 937:229

Rawh narrated to us, Abu ‘Amir al-Khazzaz narrated to us, from Abu ‘Imran al-Jawni, from ‘Abdullah ibn al-Samit, from Abu Dharr, from the Prophet, may Allah bless him and grant him peace, that he said: "Do not belittle anything of good, even if you do not find [anything to give], then meet your brother with a cheerful face."