It is narrated from Sayyiduna Abu Umamah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever goes to the mosque in the morning intending nothing but to learn or teach some good will have the reward of one who performs a complete Umrah; and whoever goes to the mosque in the evening intending nothing but to learn or teach some good will have the reward of one who performs a complete Hajj." Imam Bukhari used Thawr bin Yazid as evidence in the usul (core narrations), and Imam Muslim mentioned him among the shawahid (supporting narrations); as for Thawr bin Zayd al-Dili, he is agreed upon (as trustworthy).