Upon seeing a beautiful woman and desiring to marry her, what is the advice?

Allah has obligated His servants to lower their gaze from what He has forbidden. If a Muslim is taken by surprise by the first glance, he should not follow it with another, for the Prophet, peace and blessings be upon him, said: "Do not follow the glance with another, for the first is yours, but the second is not." If he lowers his gaze and then sees a woman whom he admires, there is no religious impediment to proposing to her. A Muslim should not live chasing desires but should be content with what Allah has provided him.