Tafsir of Al-Qiyamah 75:37

"Was he not a drop of emitted semen?" This is an inception intended to invalidate the aforementioned [denial]. Since its focus was their dismissal of the resurrection, it refutes that by [invoking] the beginning of creation.

Al-Hasan recited it as alam taku (Was she not), with the letter ta' for address, by way of iltifat (shifting of person). The majority read it as tumnā (it is emitted), with the ta' (superscript dots), in which case the pronoun refers to the drop, meaning: the man emits it and pours it into the womb. As for the reading with the ya' (yumnā), it is the recitation of Hafs, Abu 'Amr (in a narration differing from him), Ya'qub, Salam, Al-Jahdari, and Ibn Muhaysin, referring to the semen.