I went out with my father to Sham. The people of Sham would pass by the inhabitants of the monasteries and greet them with salam. I heard my father say, I heard Abu Hurayrah say, I heard the Messenger of Allah ﷺ say, "Do not initiate the greeting of salam to them, and force them to the narrowest part of the road."
حدثنا عفان حدثنا شعبة أخبرني
خرجت مع أبي إلى الشام فكان أهل الشام يمرون بأهل الصوامع فيسلمون عليهم فسمعت أبي يقول سمعت أبا هريرة يقول سمعت رسول الله ﷺ يقول لا تبدءوهم بالسلام واضطروهم إلى أضيقه
No references are available.
Suyuti narrated it in similar wording in Al-Jami al-Saghir, with the phrasing, "Do not initiate greeting the Jews or the Christians with the salam, and when you meet one of them on a road, force him to its narrowest part." Muslim, Abu Dawud, and Tirmidhi narrated it from Abu Hurairah, and Suyuti noted that it is sahih.