"None should fast one or two days ahead of the month except, someone who had a prior habit for fasting, in which case let him fast." ' (Using translation from Nasāʾī 2173)
أَنَّ رَسُولَ اللهِ ﷺ قَالَ «لَا يَتَقَدَّمَنَّ أَحَدٌ الشَّهْرَ بِيَوْمٍ وَلَا بِيَوْمَيْنِ إِلَّا أَحَدًا كَانَ يَصُومُ صِيَامًا فَلْيَصُمْهُ»