Is it obligatory for a student of knowledge to adhere solely to the madhhab of his shaykh, and when is he able to weigh between evidences?

It is better for a student of knowledge to begin studying knowledge with a شيخ (sheikh) within a specific madhhab (school of thought). However, he is not obligated to adhere to his sheikh's madhhab or the madhhab he studied in every detail. Rather, he should adhere to the Qur'an and Sunnah wherever the evidence from them becomes clear to him. When can a student of knowledge give preference between evidences in a matter? That is when he knows who possesses the faculty of discerning the aspects of preference and what has been reported in the matter from the texts of the Sacred Law and the sayings of the people of knowledge. Preferring one evidence over another should only be resorted to if it is impossible to reconcile between the evidences. Its place is in the apparent contradiction between dhanniyat (probabilistic evidences), and there is no contradiction between two qat'iyyan (definitive evidences), nor between a qat'i and a dhanni, but only between two dhanniyyan. The most important aspects of preferring are the arrangement of evidences; thus, the qat'i is given precedence over the dhanni, the text from the Qur'an and Sunnah over qiyas (analogy), and the sound hadith over the good (hasan) hadith.