The full and actual quote is "the blood of the covenant is thicker than the water of the womb," which means despite the way that "blood is thicker than water" has been held over us to value family above all else, it is the promises we make that are the most important, regardless of to whom we make them, and for me personally it means I value the friends I chose and who chose me over the clan I'm born into, if there is conflict between the two