مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2535
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn 'Abbas (رضي الله عنه) said: When the Messenger of Allah (ﷺ) came (to Madinah) they used to pay in advance for crops. He said: “Whoever pays in advance, let him not pay in advance except for a known measure and a known weight."
Musnad Ahmad 2548Its isnad is saheeh, al-Bukhari (2239) and Muslim (1604)]