As for my husband, she said, he's just that. My husband. I want that to be perfectly clear. Till death do us part. It's final. (3.36)
Here Serena Joy relies on a quotation from the marriage ceremony to remind the narrator of how little she should be able to enter into this standing relationship with the Commander. She asserts what power she has by emphasizing her status as the Commander's Wife.
Low status: he hasn't been issued a woman, not even one. He doesn't rate: some defect, lack of connections. But he acts as if he doesn't know this, or care. (4.6)
This society takes arranged marriages to a whole new level. The government decides how much action men get, if any. The fact that Nick doesn't seem to "care" about his lack of a female partner strikes the narrator as suspicious.
It's not the husbands you have to watch out for, said Aunt Lydia, it's the Wives. You should always try to imagine what they must be feeling. Of course they will resent you. It is only natural. Try to feel for them. (8.27)
Significantly, "Wives" is capitalized while "husbands" is not. Husbands have other jobs, but a Wife is a wife and a wife only. Marriage grants her a certain honorific status.
In the afternoons, when Luke was still in flight from his wife, when I was still imaginary for him. Before we were married and I solidified. I would always get there first.
I was nervous. How was I to know he loved me? It might be just an affair. Why did we ever say just? Though at that time men and women tried each other on, casually, like suits, rejecting whatever did not fit. (9.7-8)
The different kinds of relationships between men and women are contrasted here. Gilead is a first marriage-only world. An initial marriage is permanent, and there are no givebacks. At the other end of the spectrum is the time before, when "men and women tried each other on, casually." But it seems like for the narrator and Luke, marriage is what makes her "solidified," what makes her real.
To be asked to play Scrabble, instead, as if we were an old married couple, or two children, seemed kinky in the extreme, a violation in its own way. As a request it was opaque. (25.40)
The "violation" for the narrator here isn't a request for "kinky" sex or something that's otherwise outside her comfort zone. It's acting like "an old married couple" that freaks her out and makes her uncomfortable—partly because she can't figure out what the Commander wants out of it.
She disapproved of Luke, back then. Not of Luke but of the fact that he was married. She said I was poaching, on another woman's ground. I said Luke wasn't a fish or a piece of dirt either, he was a human being and could make his own decisions. She said I was rationalizing. I said I was in love. (28.3)
Whose side should we be on here, Moira's or the narrator's? Since the novel is in the first person, and the narrator is in the position of the "other woman," we tend to sympathize with her. But even though they disagree on this point, and try to take different paths, both end up in the Women's Center and at Jezebel's, so their old differences don't seem to matter in this new world.
Absurd, but that's what I want. An argument, about who should put the dishes in the dishwasher, whose turn it is to sort the laundry, clean the toilet; something daily and unimportant in the big scheme of things. We could even have a fight about that, about unimportant, important. (31.6)
The narrator craves the normalcy that was a fundamental part of her marriage, something she took for granted. Fighting about even the simplest, most trivial thing would be a privilege now.
"Behind my back," she says. "You could have left me something." Does she love him, after all? She raises her cane. I think she is going to hit me, but she doesn't. (44.17)
Serena Joy's logic is hypocritical here. She's angry with the narrator for betraying her by spending time with the Commander, but she forced the narrator to betray the Commander with Nick. Her anger here may not be justifiable, but it is human.
The regime created an instant pool of such women by the simple tactic of declaring all second marriages and nonmarital liaisons adulterous, arresting the female partners, and, on the grounds that they were morally unfit, confiscating the children they already had, who were adopted by childless couples of the upper echelons who were eager for progeny by any means. (Historical Notes.25)
Here, one of the professors explains what happened to marriages during the Republic of Gilead era, clarifying the reason the narrator was selected to become a Handmaid. Ironically, one of the biblical passages cited to support the use of Handmaids being pulled from "adulterous" relationships—the story of Rachel and Leah—clearly is about a bigamous marriage.