What is the ruling on abandoning congregational prayer in the mosque to prevent illicit seclusion (khalwa) if it leads to temptation elsewhere?

We advise the questioner to counsel his sister to leave mixed-gender work if she is not in dire need of it. As for the questioner going to the mosque and his sister remaining with two men, if he can take his sister with him to pray in the mosque, that is better, or she can wait for him outside the mosque. If that is not possible, then there is no harm in him praying in congregation with the two men at work, or with his sister in a separate place. If that is not possible, then there is no harm in him praying alone at work due to fear for his sister from seclusion (khalwah), especially if those with her do not pray, and this is one of the excuses for leaving congregational prayer. This solution should only be resorted to when all other solutions are unavailable.