Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
tabarani:9574Isḥāq b. Ibrāhīm > ʿAbd al-Razzāq > al-Thawrī > Wāṣil al-Aḥdab > Mughīrah b. ʿAbdullāh al-Yashkurī > a man

[Machine] Ibn Masud said, "Whoever breaks their fast for one day in Ramadan without a valid excuse will meet Allah with that sin, even if they were to fast the entire year. If Allah wills, He may forgive them, and if He wills, He may punish them."  

الطبراني:٩٥٧٤حَدَّثَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ عَنْ عَبْدِ الرَّزَّاقِ عَنِ الثَّوْرِيِّ عَنْ وَاصِلٍ الْأَحْدَبِ عَنْ مُغِيرَةَ بْنِ عَبْدِ اللهِ الْيَشْكُرِيِّ عَنْ رَجُلٍ قَالَ قَالَ

ابْنُ مَسْعُودٍ «مَنْ أَفْطَرَ يَوْمًا مِنْ رَمَضَانَ مِنْ غَيْرِ رُخْصَةٍ لَقِيَ اللهَ بِهِ وَإِنْ صَامَ الدَّهْرَ كُلَّهُ إِنْ شَاءَ غَفَرَ لَهُ وَإِنْ شَاءَ عَذَّبَهُ»  


See similar narrations below:

Collected by Bayhaqī
bayhaqi:8066Abū al-Fatḥ Hilāl b. Muḥammad b. Jaʿfar al-Ḥaffār> al-Ḥusayn b. Yaḥyá b. ʿAyyāsh > Ibrāhīm b. Mijshar > ʿAbīdah b. Ḥumayd > Manṣūr > Wāṣil > al-Mughīrah b. ʿAbdullāh al-Yashkurī > Ḥudditht > ʿAbdullāh b. Masʿūd

[Machine] Whoever breaks (fast) one day of Ramadan without justification, their fasting for the rest of their life will not be accepted until they meet Allah. If He wishes, He will forgive them, and if He wishes, He will punish them. Another narration from Ibn Mas'ood mentions (the same).  

البيهقي:٨٠٦٦أَخْبَرَنَا أَبُو الْفَتْحِ هِلَالُ بْنُ مُحَمَّدِ بْنِ جَعْفَرٍ الْحَفَّارُ بِبَغْدَادَ أنبأ الْحُسَيْنُ بْنُ يَحْيَى بْنِ عَيَّاشٍ ثنا إِبْرَاهِيمُ بْنُ مِجْشَرٍ ثنا عَبِيدَةُ بْنُ حُمَيْدٍ ثنا مَنْصُورٌ عَنْ وَاصِلٍ عَنِ الْمُغِيرَةِ بْنِ عَبْدِ اللهِ الْيَشْكُرِيِّ قَالَ حُدِّثْتُ أَنَّ عَبْدَ اللهِ بْنَ مَسْعُودٍ قَالَ

مَنْ أَفْطَرَ يَوْمًا مِنْ رَمَضَانَ مِنْ غَيْرِ عِلَّةٍ لَمْ يُجْزِهِ صِيَامُ الدَّهْرِ حَتَّى يَلْقَى اللهَ ﷻ فَإِنْ شَاءَ غَفَرَ لَهُ وَإِنْ شَاءَ عَذَّبَهُ وَرُوِيَ مِنْ وَجْهٍ آخَرَ عَنِ ابْنِ مَسْعُودٍ