مَنْ أُفْتِيَ بِغَيْرِ عِلْمٍ، كَانَ إِثْمُهُ عَلَى مَنْ أَفْتَاهُ
Translation: Whoever is given a religious ruling without knowledge: the sin of that [misguided ruling] lies upon the person who issued it.
Source: أبو داود
أُفْتِيَ is a passive past-tense form: “was given a ruling.” It differs from أَفْتَى, “gave a ruling.” This distinction matters: the first clause concerns the recipient, whereas مَنْ أَفْتَاهُ refers to the one who issued the ruling. بِغَيْرِ عِلْمٍ means “without knowledge.”
A fatwa is a responsible answer about a religious question. Presenting an unsupported guess as an authoritative ruling can mislead another person in worship or daily dealings, so issuing such judgments requires adequate knowledge and care.