Honestly I’d not send a message and just leave him alone. First of all mentioning that you noticed how often he logs in could make him uncomfortable. I’d not do that. Second of all you don’t know this person, there is no particular need mentioning that he doesn’t owe you anything.

Third of all If someone didn’t write you in a month, he likely doesn’t want to keep talking further. Reminding him that you are expecting a response won’t change that. I am not sure about about that religious message but I’d let the guy go