When the Vajra Sūtra tells you not to consider the Buddha as either sitting, lying, coming, or going, it is telling you not to make such distinctions. When you no longer make discriminations, your wisdom can appear. Your prajña will manifest in direct proportion to the degree you have cast out discriminations. In the minds of most people there are so many discriminations that they entirely fill the field of the eighth consciousness, which is basically pure, with filth and defilements. Once you are rid of all that garbage, your wisdom will appear.