Re: There is no compulsion in religion
I am not aware if such people were in the tribe of Banu Qainuqa, there might have been however this verse was revealed when Banu An Nadir were expelled. You cannot find this on internet sources. I found it in the Sirah by Dr. Sallabee.
It is based on the hadith in Sunan Abu Dawood:
Book 14, Number 2676:
Narrated Abdullah ibn Abbas:
When the children of a woman (in pre-Islamic days) did not survive, she took a vow on herself that if her child survives, she would convert it a Jew. When Banu an-Nadir were expelled (from Arabia), there were some children of the Ansar (Helpers) among them. They said: We shall not leave our children. So Allah the Exalted revealed; “Let there be no compulsion in religion. Truth stands out clear from error.”