Abu Dawud
Knowledge
Book Number: 019 / Hadith Number: 3649
Narated By Abu Hurairah : The Prophet (pbuh) said: If anyone is given a legal decision ignorantly, the sin rests on the one who gave it. Sulayman al-Mahri added in his version: If anyone advises his brother, knowing that guidance lies in another direction, he has deceived him. These are the wordings of Sulayman.