Musannaf Ibn Abi Shayba 27:819

Affan narrated to us, he said: Sulayman ibn al-Mughirah narrated to us, from Thabit, from Abd al-Rahman ibn Abi Layla, who said: I traveled through the garrison towns, and I did not see a town more diligent in night prayer (tahajjud) than the people of Basra.