Musnad Ahmad 30:1529

Hassan narrated to us, Hammad ibn Salamah narrated to us, from ‘Ata’ ibn al-Sa’ib, from Salman al-Agharr, from Abu Hurairah, from the Prophet, may Allah bless him and grant him peace. And Humayd, and Thabit al-Bunani, and Salih ibn Dhakwan, from al-Hasan, from Abu Hurairah, from the Prophet, may Allah bless him and grant him peace, in what he narrates from his Lord, the Almighty and Majestic, that He said: "Whoever remembers Me within himself, I remember him within Myself. And whoever remembers Me in a gathering of people, I remember him in a gathering better and purer than them."