The Noble Scholar Shaykh Sālih Al-Fawzān حفظه الله stated:
We do not obey the 'Ulamā unrestrictedly whether they are correct or incorrect. However, we follow them when they are correct and we refrain from their mistake when they are incorrect. We obey the one who obeys Allāh and we disobey the one who disobeys Allāh. We oppose the mistake of the one who is incorrect. This is the true religion.
As for (the case when) you do not know that this scholar is mistaken, you are excused. As for the one who says, “If he (the scholar) is incorrect, then his mistake is on him (and I'm still going to follow him because he is a scholar)”. We say (regarding this statement) that this is not permissible and this (position of following a scholar even if he is incorrect, saying his mistake is on him and not you) will not benefit you on the Day of Judgment.” Upon them is that which they are responsible for and upon you is that which you are responsible for.
The fatāwā (religious verdicts) are not depended upon except when they are built upon evidence from the Book of Allāh and the Sunnah of His Messenger ﷺ. Therefore, whoever knows that they are based upon other than evidence, it is prohibited for him to take them (as a position). Whoever is ignorant of this, (then) this is the one who is excused. However, it is obligatory upon him to search (for the truth) and increase in the verifying (of the facts of the matter).