مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3246
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn 'Abbas (رضي الله عنه) said: The Messenger of Allah (ﷺ) and his Companions prayed towards Jerusalem for sixteen months, then the qiblah was changed after that.
Musnad Ahmad 3270A saheeh hadeeth]