Explanation of the hadith
The foundations of holy Kaba by Ibrahim alaihis salaam and the foundation of baitul muqaddas (mosque aqsa) were not laid down by them. But they built them on the earlier foundations. There was a gap of more than one thousand years in between these two Messengers. In this Hadith, there is a narration of the foundation of both of these mosques, saying that as soon as the tauba (forgiveness) was accepted, Adam alaihis salaam laid the foundation for the holy Kaba of Allah. After forty years when his progeny increased and spread on the land, someone from them laid the foundation of baitul muqaddas. In some narrations, it has been mentioned that Adam alaihis salaam himself had laid the foundation of baithul muqaddas too after forty years of the construction of Kaba. (Miraat ul manajeeh, Volume 1, Page 710)