Allah (swt) swears by all the mankind since the creation of Adam (pbuh) and his descendants until time of Resurrection. Some scholars interpreted Allah’s saying (and which was born of him) that it refers to the barren sterile with no child. But we adopt the general meaning. The swearing by the father and that which was born of him, comes after swearing by the city, which became a city through Ibrahim (pbuh) supplication, then it became full of humans. As if the Truthful (swt) is considering His favour, upon the people of Makkah, that their city but became so by Ibrahim’s (pbuh)- the father- supplication.