It is narrated from Sayyiduna Ali (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) used to observe continuous fasting from one pre-dawn meal (suhoor) to the next, (he would not break his fast at sunset).
Hadith Referenceمسند احمد / مسند الخلفاء الراشدين / 1195
Hadith Gradingحکم دارالسلام:حسن لغيره ، وهذا إسناد ضعيف لضعف عبد الاعلي الثعلبي