Umm Haram bint Milhan, a Sahabiya, (a companion of the Prophet) was married to Ubadah ibn as-Samit Ansari. Along with her husband she undertook several trips to foreign countries. Now her grave is in Cyprus, and is called the grave of the pious woman (Hayat As-Sahaba 1/592). The grave of Khalid ibn al-Walid, who was born in Mecca, is in Hims (Syria).
The same is the case with the majority of the Companions of the Prophet. At the time of the Prophet’s demise, his companions numbered more than one hundred thousand. However it is worth noting that if you go to Mecca and Medina you will find only a small number of graves there. The reason for this is that these companions left Arabia and spread to various countries far and beyond its borders. The majority of them breathed their last in various Asian and African countries, where their graves still exist.
Why did this happen? It was because during his last days the Prophet gathered his companions together in the mosque in Medina and addressed them in these words: God has sent me as his messenger for the entire world. So you do not differ with one another. And spread in the land and communicate my message to people inhabiting other places besides Arabia. (Seerat Ibn Hisham 4/279).
It was this injunction of the Prophet that led to the Sahaba (companions of the Prophet) settling in foreign lands. In those countries either did business or earned their living by hard work, all the while communicating to their non-Muslim compatriots the message of monotheism which they had received from the Prophet. Every one of them thus became a virtual ambassador of Islam. This resulted in Islam spreading across the globe. Its evidence can still be seen in the inhabited world of that time.
I feel history is repeating itself in modern times. New circumstances, produced in the wake of industrial revolution, have resulted in Muslims leaving their homelands to spread all over the world. Today, whichever part of the globe you visit, you will find Muslims there. Mosques and Islamic institutions have come up everywhere. Muslims have settled in these countries either for work or for business. However, in respect of their religion, their actual position is that of Islam’s representatives. It is as if each one of them is an ambassador of God. Now the need of the hour is to awaken the missionary spirit in these Muslims settled in foreign lands, so that they may effectively communicate the message of Islam—a task of universal magnitude made incumbent upon them by their new sets of circumstances.