It's from a gay blogger in Australia who was doing a photo shoot of his buff friend when the LDS missionaries came by. The blogger writes:
This is pretty funny. Can you pick out the gay Mormon in the picture?
One of [the missionaries] seemed a little too happy to pose with [the bodybuilder], while the other one seemed a little scared that he might catch “sinner” if he got too close. The dark haired one even said “we saw you from a distance and I said WOW he’s BUFF”.