https://torontodawah.com/what-is-the-sunnah-concerning-congratulating-others-on-the-beginning-of-ramadaan-shaykh-abu-abdir-rahmaan-yahyaa-bin-alee-al-hajooree/
What Is The Sunnah Concerning Congratulating Others On The Beginning Of Ramadaan - Shaykh Abu Abdir Rahmaan Yahyaa bin Alee Al-Hajooree And Shaykh Saalih al-Fawzaan