Sunan an Nasai 2172
The Book of Fasting
أَخْبَرَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالَ أَنْبَأَنَا الْوَلِيدُ، عَنِ الأَوْزَاعِيِّ، عَنْ يَحْيَى، عَنْ أَبِي سَلَمَةَ، عَنْ أَبِي هُرَيْرَةَ، عَنْ رَسُولِ اللَّهِ صلى الله عليه وسلم قَالَ " لاَ تَقَدَّمُوا قَبْلَ الشَّهْرِ بِصِيَامٍ إِلاَّ رَجُلٌ كَانَ يَصُومُ صِيَامًا أَتَى ذَلِكَ الْيَوْمُ عَلَى صِيَامِهِ " .
It was narrated from Abu Hurairah that the Messenger of Allah said:"Do not fast ahead of the month, except for a man who habitually fasts, and that day happenes to be one of his regular fasts
Grading: Abu Ghuddah: Sahih · Al-Albani: Sahih · Zubair Ali Zai: Sahih - Agreed Upon
Text from the public-domain hadith-api dataset. Numbering follows that dataset and can differ by a few from some printed editions — check the wording, not only the number.