Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
quran:38:84 –

˹Allah˺ said, "The truth ˹is My oath˺, and the truth I say -  

He said, ‘So the truth is — and the truth I ˹always˺ speak (read both ˹words˺ in the accusative ˹fa’l-haqqa wa’l-haqqa˺; or with the first in the nominative and the second in the accusative because of the verb ˹aqūlu, ‘I speak’˺ that follows. As for reading the first one in the accusative, this would be on account of the mentioned verb ˹qāla, ‘he said’˺; but it is also said to be on account of its being a verbal noun, the sense being uhiqqu l-haqqa, ‘I establish the truth’; or ˹it is in the accusative by implication˺ if the particle for the oath ˹fa˺ is removed. It ˹the first haqq˺ could also be in the nominative because of its being the subject of a missing predicate, as in fa’l-haqqu minnī, ‘truth ˹comes˺ from Me’. It is also said that ˹the sentence means˺ fa’l-haqqu qasamī, ‘the truth is ˹this˺ oath from Me’, the response to which is the following ˹la-amla’anna …˺) —
القرآن:٣٨:٨٤ –

قَالَ فَالْحَقُّ وَالْحَقَّ أَقُولُ  

{قال فالحقَّ والحقَّ أقول} بنصبهما ورفع الأول ونصب الثاني، فنصبه بالفعل بعده ونصب الأول، قيل بالفعل المذكور، وقيل على المصدر: أي أحق الحق، وقيل على نزع حرف القسم ورفعه على أنه مبتدأ محذوف الخبر: أي فالحق مني، وقيل فالحق قسمي، وجواب القسم.