1205 – ʿAmr ibn al-ʿĀṣ (may Allah be pleased with him) reported that he heard the Messenger of Allah ﷺ say, “When a judge rules, applies ijtihād, and reaches the correct conclusion, he will receive two rewards; but if he rules, applies ijtihād, and then errs, he will receive one reward.” Agreed upon.⦗1⦘

Vocabulary of the ḥadith
• ḥakam: Linguistically, ḥukm (judgment) means “to prevent or restrain.” One says, “ḥakamtu ʿalayhi bi-kadha” when he is restrained from acting contrary to the ruling. Technically it is to clarify the sharʿī ruling and oblige people to abide by it.
• fa-ijtahada: Ijtihād, in its lexical sense, is derived from juhd (striving, effort). Technically it is a jurist’s exertion of his full capacity to derive a practical sharʿī ruling by means of deduction.
• akhṭaʾa (he erred): Linguistically the opposite of correctness; the term may be pronounced with a shortened or lengthened vowel and is the verbal noun of akhṭaʾa yakhṭaʾu, hence mukhṭiʾ (one who errs). Technically it is to intend something by one’s action but for the action to result in other than what was intended.
• fa-ijtahada: Coordinated to the conditional clause, i.e., “and if he intends to judge, he exerts ijtihād.”
• thumma aṣāba (then he is correct): Coordinated to “fa-ijtahada.”
• fa-lahu ajrān (he has two rewards): The apodosis of the condition.

Lessons derived from the ḥadith
1 – In technical usage, ijtihād is the exertion of one’s utmost effort to obtain the sharʿī ruling through deduction.
2 – Sharḥ al-Iqnāʿ states: The absolute mujtahid is the one who knows from the Book of Allah