On Monday, August 20, 2018, the Cubs rested. It was an off day in the middle of a road trip to Pittsburgh and Detroit on which the Cubs split six games, oddly, scoring exactly one run in each of the first five (while still managing to win two of those five!).
The Cubs had played 123 games through August 19. They then went on a stretch when, due to previous rainouts and further postponements and makeups during that stretch, they played 41 games in 43 days (including the divisional tiebreaker and the wild-card game).