It is narrated from Sayyiduna Jabir (may Allah be pleased with them both) that he said: "Do not say, 'The month has fallen short.' We fasted twenty-nine days with the Messenger of Allah (peace and blessings be upon him) more often than we fasted thirty."
Imam al-Tabarani (may Allah have mercy on him) said: "No one narrated this hadith from Muhammad bin al-Munkadir (may Allah have mercy on him) except Miswar bin al-Salt, and it is not narrated from Sayyiduna Jabir (may Allah be pleased with them both) except with this chain."
Hadith Referenceالمعجم الأوسط / باب الميم / 5445
Hadith Gradingمحدثین:إسناده ضعيف لضعف مسور بن الصلت
Hadith Takhrij«قال الهيثمي: فيه مسور بن الصلت وهو ضعيف «مجمع الزوائد ومنبع الفوائد، ج 3، ص 147»» «قال ابن عدي: غير محفوظ «الكامل في الضعفاء، ج 8، ص 182»» «أخرجه الدارقطني فى «سننه» برقم: 2352»