I recently read the second sarga of the Balakanda. At this point in the story, Valmiki has been considering the origin of his utterance on the death of the mating curlew. Brahma explains that his verse appeared from his inspiration! It’s quite a beautiful section of the text. Apologies for missing diacritics or inaccuracies.
Then Brahma, smiling, spoke to the bull-like sage: “What is created by you is none other than the śloka. Reflection on this need not be done. |30| Oh Lord [Valmiki], this speech of yours was set in motion on account of my wish alone. Great Sage, you must complete the story of the conduct of Rāma. |31| He whose soul is dharma, narrate the conduct of the wise, brave, and most-virtuous-in-the-world Rama, as the story was heard by you from Narada. |32| The conduct, both secret and known, of the wise Rama with Laksmana; the conduct of demons; and the conduct of Sītā, both known and private. That which is unknown shall become known to you. |33-34| Not a single utterance in this poem will be false. You will tell the story of Rāma, which is sacred, constructed by verse, delightful to the mind. |35| As long as there are mountains and rivers on the surface of the earth, that long the Rāmayana will circulate in the worlds. |36| And as long as the story made by you of the Ramayana will circulate, that long you will live in my words, both above and below.” |37| Having said this, Lord Brahma disappeared right then. Then, along with his student, Valmiki became amazed. |38| All of his [Valmiki’s] student sang the [first] verse again. Being pleased again and again, they spoke and were extremely wonderstruck. |39|