Reference: Siyar A’laam an-Nubalaa – Volume 20, Page 66
Abu Sa’d as-Sam’aanee said:
When I decided to undertake a journey, I visited our Shaykh, Yoosuf ibn Ayyoob, to bid him farewell.
He supported my decision [to travel], and said:
I advise you not to visit the rulers, and watch what you eat, [so you are certain] it is not haraam.