1. Gabriel was totally forced into stealing those supplies
Episode 9 picked up with Father Gabriel watching over a still and calm Alexandria. But bizarrely, the priest quickly went from quietly reading his bible to straight up breaking one of the ten commandments when he took all of the food supplies, packed up a car and made a break for it. The move seemed a little out of character from Gabriel, who really seemed to be becoming an important member of the group, and if you paid close attention you'll know that it was totally out of character because he was 100% forced into taking those action.
The first scene of the mid-season premiere picks up exactly where the post-credits scene of the mid-season finale finished. In that scene you'll remember that in that scene the mysterious "Boots" character had found his way back to Alexandria and was surveying the area. Then, if you were paying close attention to the scene in Episode 9 right before the opening credits — when Gabriel fled the community — you may have noticed that Gabriel wasn't alone in that car.
Later we learned that Gabriel had left the hidden message "BOAT" in the weapons ledger, which Rick and Aaron immediately knew meant the boat from which they had recently recovered all the supplies (a.k.a the first place we saw Boots). However, while the discovery of the message eventually lead the Alexandrians to find the new community of people, we never got to see what happened to Gabriel — is the priest still alive, or was he killed after Boots got a lift back to his community with the supplies?