Hadith 4881
وَعَن زيد بن أَرقم عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «إِذَا وَعَدَ الرَّجُلُ أَخَاهُ وَمِنْ نِيَّتِهِ أَنْ يَفِيَ لَهُ فَلَمْ يَفِ وَلِمَ يَجِئْ لِلْمِيعَادِ فَلَا إِثْمَ عَلَيْهِ» . رَوَاهُ أَبُو دَاوُدَ وَالتِّرْمِذِيُّ
Zaid bin Arqam (may Allah be pleased with him) narrates from the Prophet (peace and blessings be upon him), he (peace and blessings be upon him) said: "When a man makes a promise to his brother with the intention of fulfilling it, but he is unable to fulfill the promise and does not reach at the appointed time, then there is no sin upon him." Its chain is weak, narrated by Abu Dawood.