مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2663
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated from Ibn 'Abbas (رضي الله عنه) that The Messenger of Allah (ﷺ) stayed in Makkah for fifteen years: for seven or eight years he saw a light and heard a voice, and for seven or eight years he received Revelation. And he stayed in Madinah for ten years.
Musnad Ahmad 2680Its isnad is saheeh, Muslim (2353)]