Laudator Temporis Acti

Homer, Odyssey 16.129 (tr. A.T. Murray, rev. George E. Dimock):

Yet these things truly lie on the knees of the gods.

ἀλλ᾿ ἦ τοι μὲν ταῦτα θεῶν ἐν γούνασι κεῖται.

Cf. also Odyssey 1.267, 1.400, Iliad 17.514, 20.435.

Mark W. Edwards on Iliad 17.514:

The image is from spinning (in a sitting position) the thread of fate (ὣς γὰρ ἐπεκλώσαντο θεοὶ δειλοῖσι βροτοῖσι, 24.525), or less probably (pace Leaf) from laying offerings on the knees of seated statues...

Richard Broxton Onians, The Origins of European Thought (1951; rpt. Cambridge: Cambridge University Press, 2000), pp. 303-309, argues in favor of the explanation from spinning.

But M.L. West, The East Face of Helicon: West Asiatic Elements in Greek Poetry and Myth (1997; rpt. Oxford: Clarendon Press, 2003), pp. 222-223, offers a different explanation:

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;
let him set the Tablet of Destinies on your knees.'¹²

This may plausibly be identified as the mythological concept that underlies the Homeric phrase.

¹² Anzu III 38 f.