When the Messenger of Allah ﷺ intended to write to the Romans, and he mentioned its meaning.
حدثنا محمد بن جعفر حدثنا شعبة قال سمعت قتادة يحدث
لما أراد رسول الله ﷺ أن يكتب إلى الروم فذكر معناه
Its chain of transmission is sahih, and it has already been mentioned at 13260.