Allaamah Abdul Wahhaab Sha’raani (Rahmatullah alayh) said:
“O my Brother! Beware of consuming what is not Halaal. Consuming what is not Halaal hardens the heart, darkens the heart, prevents communion with Allah Ta’ala, and hastens old age.”
Imaam Abu Hanifah (Rahmatullah alayh) said:
"Even if a man worships Allah and becomes as thin as a rake, but he is uncaring of what enters his stomach whether Halaal or Haraam, it (his worship) is not accepted."
Ibraahim bin Adham (Rahmatullah alayh) said:
“Ensure that your food is Halaal and wholesome, then abstention from Nafl Salaat and Saum will not harm you.”
Imaam Sahl (Rahmatullah alayh) said:
“He whose food is not Halaal, the veils of darkness will not be lifted from his heart, punishments will swiftly overtake him, and his Salaat, Saum and Sadqah will not benefit him.”