Ps. 89.20-21 (Yhwh mirroring)

I found David / my servant
with my holy oil / I anointed him
whom my hand / will firmly support 
as also my arm / will make him strong. 

Yhwh now recounts the election and establishment of David as king. The movement is one of election (I “found”), to anointing, to support and strengthening. David is ‘found’ in order to be anointed king, to be missioned; he is not ‘found for himself’. This anointing and the subsequent strengthening are all in service of the mission that is being lain upon David through the covenant. 

In these opening verses we see Yhwh’s ‘fashioning’ of David, his king. Yhwh's speech is important in this regard as not Yhwh and the psalmist are mirroring each other. We saw in the opening verses how the 'hand and the arm' are described by the psalmist as Yhwh's enemy-power. They are those forces of Yhwh that he enacts in order to bring peace to his realm and to ward off the forces of chaos. Again, though, that was the psalmist's description. Here, Yhwh now refers to "my hand" and "my arm" supporting and making David strong.

It may seem like a minor point but I don’t believe so. By Yhwh mirroring the words of the psalmist there emerges the sense that Yhwh has fully ‘endorsed’ the psalmist’s recounting of his power. This mirroring will continue throughout this second portion of the psalm recounting David’s establishment. And it will lead to the devastating third portion of the psalm—where the ‘endorsement’ seems to have failed. Yhwh’s actions and the psalmist’s words will diverge dramatically. There will, in a sense, be a ‘tear’ in the fabric that is in these lines so carefully interwoven.

We should also note how David is regarded, prior to Yhwh’s ‘finding’, as Yhwh’s servant. He already exemplifies a servant-faithfulness to Yhwh (much as with Abraham and others, the covenant does not simply appear out of nowhere but follows a period of faithfulness). In the stories surrounding David this is described as David being “after Yhwh’s own heart”. He exemplifies Yhwh’s kingly concern for his realm.