Musannaf Ibn Abi Shaybah 9485 — What is mentioned on fasting Monday

Sayyiduna Ibn Abbas (may Allah be pleased with them both) was asked about fasting on Monday and Thursday, and he said: It is disliked to fix a particular day for fasting. In the narration of Yazid the wording is: (It is disliked) that one sets aside a day so that when that day comes he fasts it.