"He is more astray than the ignorant one"

Shaykh Ibn Uthaymien wrote:

والذي يفتى بلا علم أضل من الجاهل، فالجاهل يقول: لا أدرى ويعرف قدر نفسه، ويلتزم الصدق،
أما الذي يقارن نفسه بأعلام العلماء بل ربما فضل نفسه عليهم فيضل ويضل ويخطئ في مسائل يعرفها اصغر طالب علم فهذا شره عظيم وخطره كبير

ENGLISH:

"One who issues fataawa without knowledge is more astray than the ignorant one. Because an ignorant person says: "I do not know.” He knows his capability as well as being truthful. As for the one who compares himself with the most knowledgeable of scholars, rather he may even favor himself over them and in so doing he would misguide himself as well as the people, he would make mistakes in issues that even the smallest of students of knowledge wouldn’t. So the evil of this person is tremendous and his danger is great".

["Kitaab Al-Ilm", 164].