Delegation of Thaqif to Madinah

“Khalid b. Sa'id b. al-'As acted as intermediary between them and the apostle until they got their document; it was he who actually wrote it. They would not eat the food which came to them from the apostle until Khalid ate some and until they had accepted Islam and had got their document.”

Ibn Ishaq / Guillaume trans., see near 'Khalid ... acted as intermediary between them and the apostle'

“Bilal used to come to us when we had become Muslims and we fasted with the apostle for the rest of Ramadan, and bring our supper and our breakfast from the apostle. He would come to us in the morning twilight and we would say 'We see that the dawn has risen.' He would say, 'I left the apostle eating at daybreak, so as to make the dawn meal later' and he would bring our evening meal and we would say, 'We see that the sun has not entirely vanished,' and he would say, 'I did not come to you until the apostle had eaten.'”

Ibn Ishaq's Sirat Rasul Allah (via Ibn Hisham's recension, Guillaume translation) -- a member of the Thaqif deputation recounting Bilal's daily reassurance about the Prophet's suhur/iftar timing during their stay in Madinah.

“Bilal used to come to us when we had become Muslims and we fasted with the apostle for the rest of Ramadan, and bring our supper and our breakfast from the apostle. He would come to us in the morning twilight and we would say 'We see that the dawn has risen.' He would say, 'I left the apostle eating at daybreak, so as to make the dawn meal later' and he would bring our evening meal and we would say, 'We see that the sun has not entirely vanished,' and he would say, 'I did not come to you until the apostle had eaten.' Then he would put his hand in the dish and eat from it.”

Ibn Ishaq, Sirat Rasul Allah (Guillaume trans.), "The Envoys of Thaqif Accept Islam, A.H. 9", p.616