That Templar had been captured by the man who turns out to be his uncle, Saladin.  
At the end of the second act, Hafi tries to persuade the title character to accompany him to the Ganges.  In the opening scene, the title character returns home to be told by Daya that his house had been on fire during his absence.  This work has been called the "twelfth Anti-Goeze pamphlet," as it was written a few months after the author was forced to halt his controversy with Pastor Johann Goeze.  The title character's adopted daughter Recha is rescued by a Templar who falls in love with her, but they turn out to be siblings.  That Templar had been captured by the man who turns out to be his uncle, Saladin.  It is in reply to Saladin's question about the true religion that the title character tells his parable of the three identical rings.  FTP, name this play that was first performed in 1783, a work of Gotthold Ephraim Lessing.
At the end of the second act, Hafi tries to persuade the title character to accompany him to the Ganges.  
Nathan the Wise or Nathan der Weise