Most soul singers started out in the church singing gospel & lots went back to sacred music after their time doing secular stuff. It's always been there & has enjoyed periods of increased interest with soulies. From the likes of the Gospel Classics "More Love" being a biggie on the UK soul scene to "Oh Happy Day" making the pop charts & through to modern soulers getting into Donn Thomas's "How Can I Help But Love You" and more, gospel has had it's supporters. When the Staples went big on Stax and ABC took over Duke / Peacock in the 70's, gospel's profile increased. Later on, the long running CD series 'WOW GOSPEL' (which featured a compilation of the best tracks released each year) did good business for over 20 years.
But, thanks to DJ's like Greg Belson and interest from specialist reissue labels, gospel tracks seems more popular than even at the moment. With lots of 45's & LP's being recorded and pressed up in limited numbers and mainly sold at live concerts, there are plenty of rare items to lust after & chase. Just about the rarest release on the UK Chess label has to be the gospel comp album 'A Christmas Dedication From ..'. There are hundred's of US gospel 45's that would catch on if they were more widely known, many being rare items on obscure indie labels (many attached to individual churches or to the folk running choirs). There are even decent UK released gospel 45's and albums to go after on labels such as Chess, Atlantic, Action and more.
It would be good to get a few recommendations from Soul Sourcers with regard to which tracks they play on a regular basis.