Justin Bieber's flying solo! The singer attended Wednesday evening Hillsong church service WITHOUT wife Hailey Baldwin last night ... meanwhile, former flame Kourtney Kardashian was there -- with a new guy (more on that later).

Justin wore his usual Fear of God Essentials sweatpants and a Goosebumps cap as he braved the rain in order to worship. No word on where Hailey was ... but a source tells us her absence is an effort to leave space for Selena Gomez to return: "Hailey wants to pull back and allow Selena to go back to Hillsong. Hailey knows if she's there Selena doesn't feel comfortable so she'll worship on her own and put the message out that Selena can go if she wants. And all of this was Justin's idea."

Earlier in the day Justin was at his favorite restaurant -- a poke place in Beverly Hills just down the street from the his NEW HOUSE! Stay tuned for EXCLUSIVE news on the $8M mansion he and Hailey just started renting!