M.L. West (1937-2015), The East Face of Helicon: West Asiatic Elements in Greek Poetry and Myth
(1997; rpt. Oxford: Clarendon Press, 2003), pp. 222-223:
When the final outcome is yet unknown, Homer's characters will say that it 'lies on the knees of the gods' (or in the lap of the gods, as the derivative English idiom has it):
ἀλλ᾿ ἤτοι μὲν ταῦτα θεῶν ἐν γούνασι κεῖται.
There is, however, nothing in Greek myth or art to explain the phrase. 'In the gods' hands' would be easier to understand; why 'on their knees'? Babylonian poetry, while it does not possess a matching expression, nevertheless offers an attractive answer. There the future is determined by the so-called Tablet of Destinies, the ṭupšīmātu. Whoever possesses it controls the world. Its place is on its owner's knees, as we see from Anzu. After Ninurta has regained it from the usurper Anzu, Dagan is advised:
'Send for him and let him come to you;
This may plausibly be identified as the mythological concept that underlies the Homeric phrase.
let him set the Tablet of Destinies on your knees.'12
12 Anzu III 38 f.