The nobleman rode out in a carriage drawn by four horses.
Tips
culture
Famous in the proverb 一言既出,驷马难追 — 'once a word leaves your mouth, not even a four-horse team can chase it down,' i.e. a promise made must be kept. A 驷 was the fastest thing of the ancient world.
Right side 四 gives both the sound sì and the meaning at once: this is the word for exactly four horses, so the number 'four' is doing double duty as phonetic and meaning.