What is the Sharīʿah ruling concerning former salesmen opening a competing grocery store in front of their former workplace, and what is the remedy for this distress?

There is no objection to a person opening a new shop next to another shop operating in the same field, even if they had previously worked with the owner of the old shop, as there is no legal impediment to this.

However, if the intention behind opening the new shop is to cause harm to the owner of the old shop, then this act is forbidden, based on the saying of the Prophet (peace be upon him): “Whoever harms others, Allah will harm him; and whoever causes hardship to others, Allah will cause hardship to him.”

A Muslim should not preoccupy themselves with the intentions and actions of others, but rather attach their heart to Allah alone. For Allah Almighty is the Provider, and sustenance is decreed before the creation of man. No one will die until they have received their full sustenance, as the Prophet (peace be upon him) said: “Allah ordained the measures of all creatures fifty thousand years before He created the heavens and the earth,” and his saying: “Indeed, the Holy Spirit inspired in my heart that no soul shall die until it completes its appointed term and receives its full sustenance. So fear Allah and be moderate in seeking your livelihood.”

The presence of several merchants in one market indicates that each of them has their ordained sustenance. Although people may disapprove of such behavior, there is nothing in Islamic law that prevents it.