The Prophet ﷺ said: When a man makes a promise to his brother with the intention of fulfilling it and does not do so, and does not come at the appointed time, he is guilty of no sin.  

عَنِ النَّبِيِّ ﷺ قَالَ إِذَا وَعَدَ الرَّجُلُ أَخَاهُ وَمِنْ نِيَّتِهِ أَنْ يَفِيَ لَهُ فَلَمْ يَفِ وَلَمْ يَجِئْ لِلْمِيعَادِ فَلاَ إِثْمَ عَلَيْهِ  

I bought something from the Prophet ﷺ before he received his Prophetic commission, and as there was something still due to him I promised him that I would bring it to him at his place, but I forgot. When I remembered three days later, I went to that place and found him there. He said: You have vexed me, young man. I have been here for three days waiting for you. Abu Dawud said: Muhammad b. Yahya said : This is, in our opinion, 'Abd al-Karim b. 'Abd Allah b. Shaqiq (instead of "from 'Abd al-Karim from 'Abd Allah b. Shaqiq"). Abu Dawud said: In a similar way I have been informed by 'Ali b. 'Abd Allah. Abu Dawud said: I have been told that Bishr b. al-Sarri transmitted it from 'Abd Allah b. Shaqiq.  

بَايَعْتُ النَّبِيَّ ﷺ بِبَيْعٍ قَبْلَ أَنْ يُبْعَثَ وَبَقِيَتْ لَهُ بَقِيَّةٌ فَوَعَدْتُهُ أَنْ آتِيَهُ بِهَا فِي مَكَانِهِ فَنَسِيتُ ثُمَّ ذَكَرْتُ بَعْدَ ثَلاَثٍ فَجِئْتُ فَإِذَا هُوَ فِي مَكَانِهِ فَقَالَ يَا فَتَى لَقَدْ شَقَقْتَ عَلَىَّ أَنَا هَا هُنَا مُنْذُ ثَلاَثٍ أَنْتَظِرُكَ