the Prophet said: "Do not precede the month with a day nor with two days, unless that fast falls on a day that one of you would have (normally) fasted. Fast with its sighting and break fast with its sighting, and if it is cloudy, then count for thirty days, and then break (the fast)."  

قَالَ النَّبِيُّ ﷺ لاَ تَقَدَّمُوا الشَّهْرَ بِيَوْمٍ وَلاَ بِيَوْمَيْنِ إِلاَّ أَنْ يُوَافِقَ ذَلِكَ صَوْمًا كَانَ يَصُومُهُ أَحَدُكُمْ صُومُوا لِرُؤْيَتِهِ وَأَفْطِرُوا لِرُؤْيَتِهِ فَإِنْ غُمَّ عَلَيْكُمْ فَعُدُّوا ثَلاَثِينَ ثُمَّ أَفْطِرُوا رَوَى مَنْصُورُ بْنُ الْمُعْتَمِرِ عَنْ رِبْعِيِّ بْنِ حِرَاشٍ عَنْ بَعْضِ أَصْحَابِ النَّبِيِّ ﷺ بِنَحْوِ هَذَا قَالَ وَفِي الْبَابِ عَنْ بَعْضِ أَصْحَابِ النَّبِيِّ ﷺ  

the Messenger of Allah said: "Do no precede the month of Ramadan by fasting a day or two before it, unless it is the case of a man who normally performs some fast, then let him fast it."  

قَالَ رَسُولُ اللَّهِ ﷺ لاَ تَقَدَّمُوا شَهْرَ رَمَضَانَ بِصِيَامٍ قَبْلَهُ بِيَوْمٍ أَوْ يَوْمَيْنِ إِلاَّ أَنْ يَكُونَ رَجُلٌ كَانَ يَصُومُ صَوْمًا فَلْيَصُمْهُ