"Forbear" is the first word, and it works like a raised hand in a doorway. A "bold youth" has been urging a lady to marry, and the speaker steps in to stop him. The poem never says who the speaker is or what the lady wants, so everything rests on one comic, extravagant argument. She is too splendid to belong to any one person. Marriage would not honour her. It would shrink her.
The poem makes this case in the language of religion. Heaven, sacrilege, deity and god crowd into the first eight lines, and the effect is a neat trap. Love poets of the period routinely called their mistresses goddesses, and the speaker holds the suitor to his own flattery. If she really is divine, his proposal is not courtship but "sacrilege." The word "courtship" is itself slightly dismissive: what "may appear" as courtship "to others" is, to the speaker, an offence. The best joke comes with "public deity" against "petty household god." Her worshippers are the whole world, and he wants her tucked into a shrine by the fireplace. The speaker's mock-polite understatement, "were 't not very odd," makes the idea of her domestic life sound faintly ridiculous. Even the verb "dispose herself" carries a chill. It suggests that a woman who marries is being put somewhere, like an object arranged in a room.
In the second stanza the image shifts from gods to the sun, and the logic turns into a dare. "First make the sun in private shine," the speaker challenges: persuade the sun to "bid the world adieu" and keep its light for one admirer. The phrase "in compliment to you" is deliciously cheeky. It treats the sun's generosity as ordinary good manners that it might drop to please him. The speaker knows the task is impossible, so the next line allows for his "despair" and then turns it into a rebuke. If he can't tame the sun, he was wrong to try to "fix" her beams, which are "More bright and large than his." "Fix" is a good verb here. It suggests pinning down and fastening, both of which are things you cannot do to light. The poem ends on "his," so the sun gets the last word, but only as the thing she outshines.
The form keeps all this light on its feet. Each stanza is really two quatrains in one, alternating a longer line (four beats, as in "Forbear, bold youth; all 's heaven here") with a shorter one (three beats, as in "'Tis sacrilege to her"). The rhymes run ABAB: here, aver, appear, her in the first stanza and shine, adieu, confine, you in the second. The short lines work as punchlines. They land just after the longer lines have set up a claim, and the quick drop in length gives each one a little snap. The rhythm is steady and conversational, close to an iambic tread, which keeps the tone of mock-stern rebuke from turning into a lecture. The stanza about the household god ends on a question, "A petty household god?", whose final word is deliberately small after the grand words that came before.
The poem is worth reading for its wit, but also for what the wit lets it say. Judging by the text, the speaker is not simply attacking marriage. The target is the idea of reducing a remarkable woman to one man's private possession, and that point is made by playing the flatterer's game better than the flatterer can. The compliment becomes an argument. We can read the poem as sincere admiration, as teasing, or as both at once, and that ambiguity is part of its charm. In sixteen short lines Katherine Philips, a seventeenth-century poet, takes a stock gesture of love poetry, the lady as goddess, and turns it round so that it blocks the suitor's way.