Thirteen, the magic number?

Although the text does not state explicitly that the transformation from statue to divine being was a gradual process, the fact that the priest performed 13 mouth-washings and mouth-openings suggests that this was the case. If one mouth-washing and mouth-opening would have been sufficient, then why perform 12 additional mouth-washings and mouth-openings? Furthermore, note the exclamation in Incantation Tablet 4 in which the image is addressed directly, “He (Ea) has brought your divinity to completion!” (i-lu-ut-ka ú- ak-lil in ibid., 162–63, 184 line 18ab), suggesting that all 13 mouth washings and openings were necessary.—The "Image of God" in the Garden of Eden, page 56 n.79

<idle musing>
Give the poor image a break! After all, it's a long way from being a tree in the forest to becoming a god!

OK, that sounds like something Isaiah or Habakkuk might say : )
</idle musing>