Quote from Marshall in The Rough Patch
Ted: If we make Robin think for even a second that Barney is proposing, she'll lose it, and they'll break up. Marshall: That's crazy. Why don't we just, like, lead Barney into temptation? We'll find some hot woman to hit on him. [Marshall sees Barney wiping his grease-stained fingers on his shirt] Okay, the ring thing.