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.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
tabarani:17012 – And Rad b. Aḥmad b. Labīd > Ṣafwān b. Ṣāliḥ > al-Walīd b. Muslim > ʿAbdullāh b. al-ʿAlāʾ b. Zabr > Abū al-Azhar > Qām Muʿāwiyah Bidayr Misḥal al--Adhī > Bāb Ḥimṣ > Alā In al-Ṣiyām Yawm Kadhā Wakadhā Waʾinnā Mutaqaddimūn Ghad Faqām Ilayh Mālik b. Hubayrah

[Machine] I heard Abu Al-Azhar say that Muawiyah stood at the monastery of Misr on the gate of Hims and said, "Indeed, fasting is on this day and this day, and we are advancing tomorrow." So, Malik bin Hubayrah stood up to him and said, "O Muawiyah, is this an opinion you have seen or something you heard from the Messenger of Allah ﷺ ?" He replied, "I heard the Messenger of Allah ﷺ say, 'Fast the month and keep it a secret.'"  

الطبراني:١٧٠١٢ – حَدَّثَنَا وَرَدُّ بْنُ أَحْمَدَ بْنِ لَبِيدٍ ثنا صَفْوَانُ بْنُ صَالِحٍ ثنا الْوَلِيدُ بْنُ مُسْلِمٍ ثنا عَبْدُ اللهِ بْنُ الْعَلَاءِ بْنِ زَبْرٍ قَالَ

سَمِعْتُ أَبَا الْأَزْهَرِ يَقُولُ قَامَ مُعَاوِيَةُ بِدَيْرِ مِسْحَلٍ الَّذِي عَلَى بَابِ حِمْصٍ فَقَالَ أَلَا إِنَّ الصِّيَامَ يَوْمُ كَذَا وَكَذَا وَإِنَّا مُتَقَدِّمُونَ غَدًا فَقَامَ إِلَيْهِ مَالِكُ بْنُ هُبَيْرَةَ فَقَالَ يَا مُعَاوِيَةُ أَرَأْيٌ رَأَيْتَهُ أَمْ شَيْئًا سَمِعْتَهُ مِنْ رَسُولِ اللهِ ﷺ؟ فَقَالَ سَمِعْتُ رَسُولَ اللهِ ﷺ يَقُولُ «صُومُوا الشَّهْرَ وَسِرَّهُ»  

See similar narrations below:

Collected by Abū Dāwūd
abudawud:2329 – Ibrāhīm b. al-ʿAlāʾ al-Zubaydī from Kitābih > al-Walīd b. Muslim > ʿAbdullāh b. al-ʿAlāʾ > Abū al-Azhar al-Mughīrah b. Farwah

AbulAzhar al-Mughirah ibn Farwah said: Mu'awiyah stood among the people at Dayr Mustahill lying at the gate of Hims. He said: O people, we sighted the moon on such-and-such day. We shall fast in advance. Anyone who likes to do so may do it. Malik ibn Hubayrah as-Saba'i stood up and asked: Mu'awiyah, did you hear the Messenger of Allah ﷺ say something (about this matter), or is this something on the basis of your opinion? He replied: I heard the Messenger of Allah ﷺ as saying: Fast the month (in the beginning) and in the last.  

أبو داود:٢٣٢٩ – حَدَّثَنَا إِبْرَاهِيمُ بْنُ الْعَلاَءِ الزُّبَيْدِيُّ مِنْ كِتَابِهِ حَدَّثَنَا الْوَلِيدُ بْنُ مُسْلِمٍ حَدَّثَنَا عَبْدُ اللَّهِ بْنُ الْعَلاَءِ عَنْ أَبِي الأَزْهَرِ الْمُغِيرَةِ بْنِ فَرْوَةَ قَالَ

قَامَ مُعَاوِيَةُ فِي النَّاسِ بِدَيْرِ مِسْحَلٍ الَّذِي عَلَى بَابِ حِمْصَ فَقَالَ يَا أَيُّهَا النَّاسُ إِنَّا قَدْ رَأَيْنَا الْهِلاَلَ يَوْمَ كَذَا وَكَذَا وَأَنَا مُتَقَدِّمٌ بِالصِّيَامِ فَمَنْ أَحَبَّ أَنْ يَفْعَلَهُ فَلْيَفْعَلْهُ قَالَ فَقَامَ إِلَيْهِ مَالِكُ بْنُ هُبَيْرَةَ السَّبَئِيُّ فَقَالَ يَا مُعَاوِيَةُ أَشَىْءٌ سَمِعْتَهُ مِنْ رَسُولِ اللَّهِ ﷺ أَمْ شَىْءٌ مِنْ رَأْيِكَ قَالَ سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ صُومُوا الشَّهْرَ وَسِرَّهُ