The explanation of the link that I gave in the first post:
http://quran-ayat.com/pret/106.htm#a106_1
The Quraish tribe inhabited Mecca which was (and still it is) devoid of plants and vegetation. Mecca is the city including the Inviolable House of God to which people go for pilgrimage and to worship God alone without associate or peer.
When Prophet Abraham settled his wife Hagar with her son Ishmael the first born of Abraham; so he settled them in Mecca near the Inviolable House of God to which people went for pilgrimage and to worship God in His house of worship.
Abraham knew it was devoid of vegetation and plants, but worked according to God's command, and he prayed God to bless them and to provide for them good and much provision.
The Arab respected the House of God, and none of the Arabs and the non-Arabs dare to transgress on God's House at Mecca, especially after the destruction of Abraha and his host with his elephant.. so God Almighty tore them up (as will He tear up the Zionists if they dare transgress on the Aqsa Mosque at Jerusalem.)
Prophet Abraham had also sons from Keturah his wife other than Ishmael (father of the Arab of Mecca) and Isaac (father of Jacob: Israel);
some of his sons dwelled in Midian in Siani where Moses went when he fled Pharaoh and he resided in Midian for 8 years and he married there.
Therefore, the people of Mecca started to trade and their caravans went north to Syria and Palestine in Summer, and they went south to Yemen in Winter.
By this way they got their means of livelihood: they communicated with India, China and Abyssinia and they carried these goods and commodities to Mecca and to Syria and Palestine, and they carried the goods of the Greek and Europe from Syria and Palestine to Yemen in their journeys.
So while the European empires in Greece and Rome fought with the Persian empires with their devastating wars... the caravans of Mecca went on and none dare touch their trade because they were the custodian of the Inviolable House of God at Mecca to which people went for pilgrimage and worship.
Therefore these two journeys in Summer and Winter vouchsafed the livelihood of Meccans and the Arab and provided the surrounding countries with some essential goods.
Soora 106
(In the name of God, Most Gracious, Most Merciful)
1. For the composing
a of the Quraish [tribe, there are reasons];
[Then God – be glorified – described the reasons for such unity and friendship, and He said:]
2. [The reason for] their composing is the [two trading] caravan-journeys in winter and in summer.
b
3. So they should worship the Lord of this House [: the Ka'aba at Mecca.]
4. Who has fed them against hunger,
5. And has secured them, relieving them from all fear [from the enemy.]
c
.....................................................................................................................................................................
a It means the friendship and unity.
b It means: These two caravan journeys for trading were the reason for the composing of the tribe of Quraish; for there was a caravan journey in summer to Levant for trading, and another caravan-journey in winter to Yemen for trading also; and by means of this, they gained their means of livelihood.
In addition, they were secure in Mecca, for they were the guardians of the House [of God] so that none may attack them.
c That was because Abraha terrified them when he came with his army to Mecca and intended to demolish the Ka‘aba, but God sent against them the birds: the black ravens to shoot them with stones, and He dispersed their host, and by this way the people of Mecca were relieved from fear, and none transgressed on them afterwards.
Here is also the nice recitation of this great soora of the Quran
en.m.wikipedia.org
