In Likutei Moharan 1:8:2 Rabbi Nachman says:
(Source From Sefaria.org)
כי כנור של דוד היה של חמש נימין, כנגד חמשה חמשי תורה
[King] David's Lyre had 5 strings, corresponding to the 5 books of the Torah
Is there a source from which Rabbi Nachman is drawing from to say that King David's Lyre had 5 strings? Or is this his own original idea?