In Herbert's day, a harbinger was an advance officer who went ahead of an important household and marked the doors of lodgings it meant to take over. Herbert turns that figure into a poem about growing older. "White is their colour, and behold my head": the intruders seem to be grey hairs, forerunners of age, come to requisition the mind. Herbert was a seventeenth-century English clergyman, and the poem's real subject is what a religious poet might lose as his powers fade, and whether it matters.
The first stanza is anxious. "Must they have my brain?" he asks, and the pun in "dispark / Those sparkling notions" shows how much he is afraid of losing. To dispark is to throw open an enclosed park, so his private garden of wit is about to be trampled. The stanza ends with "Must dulnesse turn me to a clod?", a short line that drops from ten syllables to eight and feels like a stumble. Then comes the pivot, "Yet have they left me, Thou art still my God." That sentence returns, almost like a refrain, in the second and last stanzas, and each time it steadies the poem.
The harbingers, it turns out, have spared "my best room, / Ev'n all my heart," and Herbert's house metaphor lets him shrug off the rest. The shrug is not quite sincere. He keeps addressing his own "sweet phrases, lovely metaphors" as if they were servants about to desert him, and his tone swings between wounded and teasing. Their past is described bluntly: they once "knew the doores" of "stews and brothels," until he washed them with tears and "brought [them] to Church well drest and clad." Poetic skill, in this account, is something he rescued, cleaned up and put to work for God. The fourth stanza gets almost playful, with "sugar-cane, / Hony of roses" about to run off with "some fond lover" and end up in "a stie." His mock-scolding, "Fie, thou wilt soil thy broider'd coat", sounds like a parent chasing a child in its best clothes.
Formally, the poem is very controlled. Each stanza of six lines rhymes ababcc, and the fifth line shortens to tetrameter before a pentameter line closes the stanza. The closing couplets do the heavy lifting, and in the second stanza the feminine rhyme "dittie / wittie" gives a slightly cheeky lift: if God likes the song, then it is "fine and wittie" by definition.
The fifth stanza is the argument at its most serious. Foolish lovers can cover their shame "with canvas, not with arras", coarse cloth instead of rich tapestry, but "True beautie dwells on high: ours is a flame / But borrow'd thence to light us thither." Earthly beauty is only a borrowed light that points back to its source, which is why "Beautie and beauteous words should go together." Herbert is not rejecting ornament here. He is defending it, as long as it serves that purpose.
The last stanza then lets it go. "Go birds of spring: let winter have his fee," he says, and the image of the harbinger's chalk returns as "a bleak palenesse chalk the doore." The earlier panic is gone. Everything fancy that the phrases might say, he realises, is already contained in "Thou art still my God, is all that ye / Perhaps with more embellishment can say." The closing wish, "So all within be livelier then before," suggests that the inner life may grow brighter as the outer decoration fades.
The poem is significant for its irony and its honesty. It is a farewell to eloquence written in thoroughly eloquent language, full of metaphor, wordplay and neat rhyme. It says it can do without these gifts while showing how good they are. Herbert also does not pretend that giving up ornament is painless. He argues with himself, bargains, scolds and finally accepts. For a student, it is a good example of a poem thinking aloud about what poetry is for, and arriving at an answer plain enough to fit into six words.