It has a reference that the destruction of Abraha and his army was for saving Allah’s (swt) House, then for Quraish accustomed security in the two journeys in summer and in winter, so that, they were able to provide sustenance, with no hunger, and safety, with no fear.
Because they are indebted to the Lord of this House and the House, so that they had to repay the favour by worshiping of the Lord of this House, whose favour was the reason of their safety and happiness.
فَلْيَعْبُدُوا (Let them worship): The act of worshipping has many ways and each one has its reference. Allah (swt) says:
﴾وَمَا خَلَقْتُ الْجِنَّ وَالْإِنسَ إِلَّا لِيَعْبُدُونِ ﴿
(And I did not create the jinn and mankind except to worship Me.) (Adh-Dhariyat: 56)
Worship exists in all aspects of life; A worker in the factory, if he works faithfully, then he is in worship, a farmer in the field, if he works skillfully, then he is in worship, the clerk in his job, if he works sincerely, then he is in worship…. This is because worshipping is not limited to fast, pray, pilgrimage and giving alms, these are the pillars of Islam, the Prophet (saws) said:
“Islam is built on five (pillars): Testimony that there is none worthy of worship except Allah, establishing Salah, giving Zakah, Hajj, and fasting Ramadan.”
While Islam is all what Allah (swt) commanded and forbid, the worship is every good deed that benefits the human being, his community, his country and all the humanity in general. This is the worship that Allah (swt) wants from us by saying (Let them worship).
 Sahih Al-Bukhari, Book of faith, Hadith No. 8.