In plain words
The poet, to the Lord: O our Lord! You became the letters, the thirty-three consonants, the sixteen vowels and five letters more; you are the one the three Vedas speak of, and the meaning of the twelve-syllable mantra [three, three, three and three]; you are the light that shines in the three syllables [of Om], and the lamp that never wavers [its first letter, a]. Taking it on yourself as your own work, you entered my heart: what simplicity is this!