مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3324
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated from Ibn Abi Mulaikah that Ibn 'Abbas (رضي الله عنه) wrote to him (saying): The Messenger of Allah (ﷺ) said: “The one against whom a claim is made is more entitled to swear an oath."
Musnad Ahmad 3348Saheeh hadeeth]