How can we understand the Hadith: "If the man's fluid overrides the woman's fluid, it will be a male, by the will of Allah; and if the woman's fluid overrides the man's fluid, it will be a female, by the will of Allah," which indicates gender determination before fertilization, alongside the Hadith Qudsi that indicates gender determination occurs after fertilization, when the angel asks Allah on the fortieth day, "O Lord, is it male or female?"

The hadith (definition) of Hudhayfah ibn Usayd al-Ghifari explains that the angel shapes the embryo and determines its sex after forty-two nights. As for the gendering of the fetus and its relation to the man's and woman's fluids, it is mentioned that the man's fluid is alkaline and the woman's fluid is acidic, and that the dominance of one over the other determines the sex of the newborn based on its effect on sperm motility. It has been scientifically proven that sex determination depends on the meeting of chromosomes.