In The Flash Season 3, there are a couple of episodes (such as 3x06 "Shade" and 3x11 "Dead or Alive") where H.R. and later Cisco have said a rhyme that goes like this:
"If a string is in a knot, patience will untie it. Patience can do lots of things, have you ever tried it?"
Is this a reference to something? Unfortunately, searching online only turns up irrelevant results or copies of the show quote for me.