Sahih Muslim
The Book Giving Description of the Day of Judgement, Paradise and Hell (Kitab Sifat Al-Qiyamah wal Janna wan-Nar)
Book Number: 039 / Hadith Number: 6777
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).