Sefer HaBahir 28

1They said to him [Mar Rachumai], "What is Hei? He was angry and said to them, "Did I not say to you not to ask me about a later thing and afterward about the previous?" They said to him, "But Hei is written after [Dalet]!" He said to them, "It is fitting for it to have been written, ' Gimmel Hei,' so why is it written, ' Gimmel Dalet'?" He said to them, "The Gimmel was switched in place of Dalet, in the head in the place of Hei. Dalet in the embellishment of the place of Hei."