“By the fig and the olive,

By Mount Sinai,

By this city of security (Makkah),

Surely we have created man of best stature,

The we reduced him to the lowest of the low,

Except those who believe (Islamic Monotheism) and do righteous deeds. Then they shall have a reward without end.

Then what causes you to deny the recompense (day of Resurrection)?

Is not Allah the best of judges?”

Surat At-Tin, Qur'an 95:1-8

Allah swears by holy places, places where revelations came down to His Prophets. First of those places is Ash - Sham (Syria) in general and Jerusalem in particular, for figs and olives grow in the area. It is as if Allah is swearing by the message that was revealed to Prophet Isa (phuh).

Mount Sinai is in the area of Sinai. It is as if Allah is swearing by the message that was revealed to Prophet Musa (phuh) on Mount Sinai ; 'Sinin' mentioned in the verse above. 

And 'this city of security' refers to Makkah Al Mukarramah which is where Prophet Muhammad (PBUH) received Revelation.

Therefore, it is as if the Verses are oaths taken by the divine messages that were revealed to the Prophets. This points to the spirit of brotherhood between the Prophets for though the laws they came with differed, their religion was one - the religion was Islam.

(Information obtained from Atlas of the Quran)