How does one greet those who pass by a place where there are both disbelievers and Muslims?

Question:
We are in an age where disbelievers and Muslims are mixed together, so the one who passes by some workers cannot distinguish between these and those. How does he greet them if he is in doubt about it?

Answer:
If Muslims and disbelievers are in a country, the scholars have decided that it is necessary for the disbelievers to have a mark by which they are known. When 'Umar ibn al-Khattab was granted by Allah the opening of the lands of Sham, he ordered that there be a mark distinguishing the Christians and the Jews from the Muslims. The mark is to be on their necks or on their clothes so that they are known by it, so that they are not confused with Muslims, and so that they do not initiate the salam to them. It is not for the foot of a Muslim to come upon Muslims; rather, the one in authority should see something by which they are known, so that the Muslim worker can distinguish between the Christian workers. Yes.