Musannaf Ibn Abi Shayba 3:5720

Mu'adh ibn Hisham narrated to us, he said: Sufyan narrated to us, from 'Ayyash al-'Amiri, from 'Abdullah ibn Shaddad, he said: When the Prophet, may Allah bless him and grant him peace, would perform the taslim, some Bedouins from Banu Tamim would say: "O Allah, grant us wealth and children." Then [the verse] was revealed: "And do not recite [your prayer] too loudly."