Al-Kāfi

Hadith 786
oaths-vows
14- أَحْمَدُ بْنُ مُحَمَّدٍ عَنِ ابْنِ فَضَّالٍ عَنِ ابْنِ بُكَيْرٍ عَنْ زُرَارَةَ عَنْ أَبِي جَعْفَرٍ (عَلَيْهِ السَّلام) قَالَ قُلْتُ لَهُ الرَّجُلُ يَحْلِفُ بِالأيْمَانِ الْمُغَلَّظَةِ أَنْ لا يَشْتَرِيَ لأهْلِهِ شَيْئاً قَالَ فَلْيَشْتَرِ لَهُمْ وَلَيْسَ عَلَيْهِ شَيْ‏ءٌ فِي يَمِينِهِ.
14. Ahmad ibn Muhammad has narrated from ibn Faddal from ibn Bukayr from Zurarah who has narrated the following: “I once asked abu Ja‘far (a.s.), about the case of a man who takes an oath very seriously not to buy for his family. He (the Imam) said, ‘He must buy for them and he does not owe anything because of his oath.’”
Source: Shaykh Muḥammad b. Yaʿqūb al-Kulaynī