The first stanza of "The Faithless Wife" by Federico García Lorca describes circumstances leading up to the incident that occurs later. The speaker, narrating a first person, personal experience, without really telling his feelings while he narrates events and his impressions, tells that he took a woman to the river who said she was a virgin although she had a husband. The reason for this seems to be reflected in the later lines "but I did not fall in love / for although she had a husband..." It seems the unfaithful wife's desire was to seduce the speaker who describes himself later on as a Gypsy.
He also declares that it seemed he was almost obligated to take this wife, who claimed to be virgin, to the river for a seduction of intimacy. His corroboration is to state that it was St. James night. St. James, along wiht being the Apostle John's brother, was one of three chosen to witness Jesus' Transfiguration. The allusion is to the "nard," "mother of pearl" and "nacre" transformation the speaker will witness later by the river.
He also describes the crickets, providing orchestral choral tones; her uninhibited responsiveness; and the breaking down of physical barriers as her petticoat seemed to be torn by "tens of knives." What may seem at first reading to be a foreshadowing of warning in large trees and barking dogs, is actually part of the reason for the experience feeling "obliged": the silver lighted enlarging trees and the dogs barking as on sentinel duty "far from the river" are benediction and protection.
The second stanza describes how they undressed, with a bit of irony as she removes "her four bodices." She is likened to spikenard ("nard"), an herb growing in the Himalayas with a rose purple blossom; to mother-of-pearl, a luminescent lining in some mollusk shells; to a silvered glass; and finally to a mother-of-pearl ("nacre") mare (female horse).
The next-to-last stanza, one two final short stanzas, describe their retreat from the river and ends with an allusion to the duel the Gypsy would surely have had with the husband after the seduction of a woman who claimed to be married. The Gypsy ends by saying that, true to Gypsy ways, he gave her a small parting token gift and more importantly, by saying that he didn't fall in love with her. the phrasing using "for" functioning like "because" suggests that Gypsies never fall in love with maidens. This way, she gains her goal and he avoids that duel with something other than lilies battling in the air.