"The fair breeze blew, the white foam flew,
The furrow followed free:..."
See in text (The Rime of the Ancient Mariner in Seven Parts)
Coleridge uses a lot of words that start with the letter f in this stanza for expressive purposes. Repeating letters at the start of words is called alliteration. Try reading this passage out loud. All of those f-sounds imitate the sound of a blowing wind.