1 Corinthians 2:10

2:10 God has revealed these to us by the Spirit. For the Spirit searches all things, even the deep things of God.

Romans 11:33-34

11:33 Oh, the depth of the riches and wisdom and knowledge of God! How unsearchable are his judgments and how fathomless his ways!

11:34 For who has known the mind of the Lord,

or who has been his counselor? ¹ 

¹ sn A quotation from Isa 40:13.