Jami` at-Tirmidhi 685
جامع الترمذي#685SahihAbu Hurairah narrated that :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
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Bashar Awad MaaroufHasan Sahih
Zubair Ali ZaiSahih Muslim
In-book reference: 8:4