Except for those who connect it with what is before it (i.e. first half), or ˹fasted˺ out of a regular habit. His ﷺ habit was to fast on Mondays and Thursdays, so it agreed with ˹the recommendation˺.
إلا لمن وصله بما قبله، أو وافق عادة كان عادته صوم الاثنين والخميس فوافقه
The Prophet ﷺ said, "None of you should fast ˹a voluntary fast˺ a day or two before the month of Ramadan unless he has the habit of fasting ˹such days voluntarily˺ then he may fast that day."
عَنِ النَّبِيِّ ﷺ قَالَ: «لاَ يَتَقَدَّمَنَّ أَحَدُكُمْ رَمَضَانَ بِصَوْمِ يَوْمٍ أَوْ يَوْمَيْنِ إِلاَّ أَنْ يَكُونَ رَجُلٌ كَانَ يَصُومُ صَوْمَهُ فَلْيَصُمْ ذَلِكَ الْيَوْمَ۔»
the Messenger of Allah said: "Do not fast before Ramadan. Fast with its sighting, and break fast with its sighting, and if it is obscured from you due to a cloudy sky, then complete thirty days."
قَالَ رَسُولُ اللَّهِ ﷺ: «لاَ تَصُومُوا قَبْلَ رَمَضَانَ: صُومُوا لِرُؤْيَتِهِ، وَأَفْطِرُوا لِرُؤْيَتِهِ۔ فَإِنْ حَالَتْ دُونَهُ غَيَايَةٌ فَأَكْمِلُوا ثَلاَثِينَ يَوْمًا۔»
the Messenger of Allah ﷺ said: "When one half of ˹the month of˺ Shaʿbān remains then do not ˹continue to˺ fast."
قَالَ رَسُولُ اللَّهِ ﷺ: «إِذَا بَقِيَ نِصْفٌ مِنْ شَعْبَانَ فَلاَ تَصُومُوا۔»
We were with Ammar b. Yasir when a roasted sheep was brought and he said: "Eat." Someone among the people said: "I am fasting." So Ammar said: "Whoever fasts on a day in which there is doubt, then he has disobeyed Abu al-Qasim ﷺ."
كُنَّا عِنْدَ عَمَّارِ بْنِ يَاسِرٍ فَأُتِيَ بِشَاةٍ مَصْلِيَّةٍ فَقَالَ كُلُوا فَتَنَحَّى بَعْضُ الْقَوْمِ فَقَالَ إِنِّي صَائِمٌ فَقَالَ عَمَّارٌ مَنْ صَامَ الْيَوْمَ الَّذِي يَشُكُّ فِيهِ النَّاسُ فَقَدْ عَصَى أَبَا الْقَاسِمِ ﷺ