Mishkat al-Masabih 15 Oaths and Vows كتاب الإيمان والنذور 11

وَعَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «الْيَمِينُ عَلَى نِيَّةِ الْمُسْتَحْلِفِ» . رَوَاهُ مُسلم

He reported God’s Messenger as saying, “An oath is to be interpreted according to the intention of the one who takes it.” Muslim transmitted it.