Sahih Muslim Book 39, Hadith Number 6777.
Chapter : Moderation in giving sermon.
Shaqiq b. Wi’il reported that ‘Abdullah used to give us sermon on every Thursday. A person said: Abu ‘Abd al-Rahman, we love your talk and so we yearn (to listen to you) and earnestly desire that you should deliver us lecture every day. Thereupon he said: There is nothing to hinder me in giving you talk (every day) but the fact that you may be bored. Allah’s Messenger (may peace be upon him) did not deliver sermons on certain days (fearing that we might be bored).