مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2285
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn 'Abbas (رضي الله عنه) said: Allah enjoined prayer on the lips of your Prophet (ﷺ), four (rak'ahs) when not travelling, two rak'ahs when travelling, and one rak'ah at times of fear.
Musnad Ahmad 2293Its isnad is saheeh, Muslim (687)]