The episode opens with members of another SG team running from what appear to be a jungle tribe, and trying to return to the gate. One of the members is stuck down by a poison dart, and the other manages to dial Earth, but does not go through. We find out that a crazed SG member has taken over leadership of the tribe, and the other members of his team were trying to warn the SGC about it. SG-1 is sent through to find out what happened to the team. They find the remaining member who survived and find out that their leader has lost his mind and considers himself the god of the tribe.
We find out that the planet has deadly solar radiation, so the people live in caves and only come out during the night. The team is then attacked at night and the SG-9 member is captured. SG-1 approaches the caves to find a vast number of people working to build a temple, which has been ordered by the SG commander. Carter believes she can get close to him as they were once engaged. She allows herself to be captured and tries to talk sense into the commander. He believes that he is the savior of the people and their god, and by building a temple, they can reclaim their world and civilization (and he also has found a Goa'uld device which is believed to block the deadly radiation). He commands Carter to figure out how it works so he can turn it on and be worshiped.
Meanwhile O'Neill, Daniel, and Teal'c isolate a member of the tribe and find out what is going on. They find out that there used to be two devices which created a force field to block the radiation. They set out and find the second device, and Teal'c and Daniel work at getting it to work. O'Neill returns to the caves to rescue the member of SG-9 who has been tied to a post in the sun as punishment. O'Neill is captured and we see Carter getting the device to work. The commander decides to set up a show to prove his power. He brings the people to the stargate, which has been rather conveniently placed sideways on the ground. He is going to execute the two demons, O'Neill and the member of SG-9, by dialing Earth but not sending the iris code, and tossing them in. He then turns on the device, but nothing happens since the second one is not on. Daniel and the tribe member interrupt by blasting the guards who are going to push in O'Neill, and proving that the commander is no god. The tribe revolts, grabs him, and throws him into the stargate. SG-1 then leaves the people to enjoy their world now that the radiation is blocked.
"The First Commandment" provides examples of the following tropes:
- An Aesop: Part of the first-season weirdness. During the epilogue, Jack explains he doesn't remember much of The Bible besides the commandment against killing (mistakenly thinking it's the eponymous first commandment), saying that killing people pushes you closer to being like Hanson.
- The Alleged Boss: O'Neill lampshades this is reference to himself when first Carter and then Connor refuse to follow an order in quick succession, leading to the infamous line:O'Neill: Does it say Colonel anywhere on my uniform?
- As the Good Book Says...: The First Commandment in The Bible is "Thou shalt have no other gods beside Me (the LORD)", hence the title, which Carter quotes when Jack says that what he thinks is the First Commandment is about the only part of the scripture he remembers. In fact, Jack has confused it for the Fifth/Sixth Commandment (depending if you're a Catholic or a Protestant), "Thou Shalt Not Kill" (which is better translated as "Thou shalt not murder").
- Attack Hello: Connor does this to Daniel, mostly due to being traumatized and delirious from prolonged exposure to the sun. And then O'Neill responds by pulling the same move on Connor.
- Big Damn Heroes: Daniel and Jamala show up to save the day just as O'Neill and Connor are about to be sacrificed.
- Black Dude Dies First: It seems as though this will be played straight with Connor in the cold open, but he is ultimately the only member of his team to survive.
- Cruel and Unusual Death: Anyone who displeases Hanson is tied to a stake and left out in the sun, which gives off dangerous amounts of radiation on this particular planet. If they manage to survive for seven days then they're released, but by that time they're usually blinded and so severely burned that they wind up dying anyway.Connor: Personally, I'd rather eat a bullet.
- Domestic Abuser: Implied to be the case with Carter and Hanson's former relationship.Carter: Jonas likes control.
- Dramatic Necklace Removal: Hanson rips off his dog tags when informed that SG-1 are coming after him.
- A God Am I: Jonas Hanson initially took on a God Guise despite SGC policy, arguing that it would make interacting with the locals easier if they just went along with their initial misconception. He later became the mask as a result of spending so long in the sun looking for a lost child that he suffered brain damage.
- Ironic Echo: Daniel commenting that food he's been offered "tastes like chicken" hearkens back to a compliment he pays the Abydosians in the movie. In this case, he's complaining about US military rations, specifically because he's not eating chicken.
- Lost Aesop: The aesop for this episode, according to Jack, is "Thou Shalt Not Kill",note arguing that every time you do, you get a little closer to being like Jonas. This already doesn't make much sense considering the Jonas was just killed by his worshipers when they turned against him, but this message is also placed in a Military Science Fiction series where the protagonists are literally US Air Force personnel and are in combat roughly every other episode. The series rarely attempted an outright "message episode" ever again.
- One-Steve Limit: Averted; another Jonas shows up much later on and plays a vastly more significant role.
- Permission to Speak Freely: Said by Connor before he tells the team exactly how far off the deep end Hanson has gone.
- Shout-Out: Of the musical variety. Near the end of the episode, the theme from Independence Day is briefly used, possibly as a nod to the origins of Stargate.
- Tastes Like Chicken: MREs never fail to lower one's expectations for cuisine.Daniel: This tastes like chicken.
Carter: So what's wrong with it?
Daniel: It's macaroni and cheese. - Thou Shalt Not Kill: Referenced at the end of the episode, when O'Neill is consoling Carter about her inability to kill Hanson.
- Two-Keyed Lock: It's revealed that there are two devices, both of which need to be activated for the forcefield to work.
- The Unsmile: Daniel encourages Teal'c to smile in order to reassure Jamala that they're friendly. The result is... unsettling.
- What You Are in the Dark: Hanson wagers that Carter will be unable to kill him in cold blood, even though they're alone and she has a loaded gun trained on him. He's right.
