Sunan an-Nasa'i, Volume 3, Book 22, Hadith 2237 (DarusSalam) ⓘ
It was narrated that Al-Walid bin Abi Malik said: "Our companions narrated to us that Abu 'Ubaidah said: 'Fasting is a shield, so long as you do not damage it."'
أَخْبَرَنَا مُحَمَّدُ بْنُ حَاتِمٍ، قَالَ أَنْبَأَنَا حِبَّانُ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ، عَنْ مِسْعَرٍ، عَنِ الْوَلِيدِ بْنِ أَبِي مَالِكٍ، قَالَ حَدَّثَنَا أَصْحَابُنَا، عَنْ أَبِي عُبَيْدَةَ، قَالَ الصِّيَامُ جُنَّةٌ مَا لَمْ يَخْرِقْهَا .
also referenced under: Hadith 2235 (Reference) & Book 22, Hadith 146 (In-Book)