The fourth line crosses into the upper trigram, Kan, the Abysmal itself, and the image shifts from approaching danger to being caught inside it: waiting in blood, a phrase every major translation preserves because there is no gentler way to render it. This is the pit, or the edge of it, and the line text's counsel is unusual for the hexagram: rather than more patience, it calls for withdrawal, coming out of the hole one has fallen into rather than continuing to endure it.
The distinction matters. Lines one through three counsel holding a position while danger approaches; line four, already within danger, counsels leaving the exact spot where one is caught, since remaining still where the ground has already given way is no longer the disciplined waiting the hexagram otherwise recommends.
Read against the sequence of images, blood marks the low point of the hexagram's approach to Kan, the moment the abstract danger of the upper trigram becomes concrete and personal, and the fact that escape is available at all, simply by yielding the untenable ground, is itself part of the hexagram's larger argument that patience is a method, not an endurance test to be carried past the point of use.