Musannaf Ibn Abi Shayba 3:749

Abu Bakr narrated to us, he said: Abu Khalid al-Ahmar narrated to us, from Hajjaj, from Abu Ishaq, from Abu al-Ahwas, from Abdullah, who said: "When the Imam says the taslim, then stand up and do whatever you wish." He says: Do not wait for his standing, nor for his moving from his place of sitting.