Imaam ash-Shaafi'ee (rahima-hullaah) said:

((The Sunnahs of the Messenger of Allaah (sal-Allaahu `alayhe wa sallam) reach, as well as escape from every one of us. So whenever I voice my opinion, or formulate a principle, where something contrary to my view exists on the authority of the Messenger of Allaah (sal-Allaahu `alayhe wa sallam), then the correct view is what the Messenger of Allaah (sal-Allaahu `alayhe wa sallam) has said, and it (that) is my view)).

Related by Haakim with a continuous sanad up to Shaafi'i, as in Taareekh Damishq of Ibn 'Asaakir (15/1/3), I'laam al-Muwaqqi'een (2/363, 364) & Eeqaaz (p. 100)

Ref: Fatwa-Online

Shaykhul Islaam Taqee ad-Deen ibn Taymiyyah said:

"If the source of this person’s wealth is not known then it is not forbidden to eat [take] from him. However, if it is known that this person’s wealth has been…"

Ref: Eating from lawful and unlawful sources