strike while the iron is hot

The adage originates from the craft of blacksmithing, predicated on the necessity of shaping metal before it cools and loses its malleability. It appears in the late 14th century in Chaucer’s The Tale of Melibee, which contains the instruction, "right so as whil that iren is hoot men sholden smyte."

The phrase acquired a secondary, more specific association through the activities of Joseph Paisley, a blacksmith at Gretna Green. Paisley served as a "priest" for eloping couples, performing marriage ceremonies over his anvil to accommodate those in a hurry to wed. The use of the motto in this context suggests that in matters of matrimony, as in metallurgy, delays are generally ill-advised.