‘I know Ephraim,
And Israel is not hid from me,
For now, O Ephraim, you have played the harlot,
Israel is defiled.
‘Their doings will not allow them,
To turn to their God,
For the spirit of whoredom is within them,
And they do not know YHWH.'
There is an interesting inclusio and play on ideas here in that YHWH is said to ‘know Ephraim' (Israel) whilst Ephraim and Israel ‘do not know YHWH'. YHWH is omniscient and Israel are blind. The idea behind YHWH knowing Israel is that nothing that they do is hidden from Him (so the parallel). He is aware of all that they do. As a consequence He is fully aware of their idolatry and their playing the harlot after false gods. And the result is that their behaviour will not allow them to turn to the One Who is truly their God. This is because they are possessed with the spirit of whoredom and as a consequence do not have the true knowledge of YHWH.
Note how the change from personal address by YHWH to a third person reference to Him brings out that they no longer have any relationship with ‘their God'. They have lost Him, and now have no place before Him.