Does the slave girl whose wrist a man touches from the river al-Baydakh become his wife, or is she for pleasure then returns to the river?

Ibn al-Qayyim transmitted this narration from Ibn Abbas verbatim, and al-Suyuti attributed it to Ibn Abi al-Dunya with a different wording: "Indeed, in Paradise, there is a river called al-Bidakh, over which are domes of ruby. Beneath it are maidens growing. The people of Paradise will say, 'Let us go to al-Bidakh!' So they will come and examine those maidens. If one of them is pleased with a maiden, he touches her wrist, and she follows him, and another grows in her place."

If this narration is authentic, it appears that whoever chooses a houri will have her as his wife, and she will not return to her place, as understood from "and another grows in her place" and the verse: "So it is, and We will marry them to houris with beautiful, wide eyes." This narration, if authentic, has the ruling of being مرفوع (raised to the Prophet), as it concerns matters of the unseen. However, no statements from scholars regarding its chain of transmission have been found.