Authentic
graded by Al-Albani
Mishkat al-Masabih 3416
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.
Cited in Mishkat al-Masabih (No. 3416).