Not because of your righteousness or the uprightness of your heart are you going in to possess their land, but because of the wickedness of these nations the LORD your God is driving them out from before you, and that he may confirm the word that the LORD swore to your fathers, to Abraham, to Isaac, and to Jacob. Deuteronomy 9:5 (ESV)
God reminds the people that it is not by their own righteousness that they are given the land. It is God who goes before them and he seeks to confirm his own word. It is the same for us, we are saved by Gods Grace, not by our own righteousness. Ephesians 2:5, 8
Circumcise therefore the foreskin of your heart, and be no longer stubborn. Deuteronomy 10:16 (ESV)
God points to the true meaning of circumcision, it was a sign pointing to cutting unclean and evil things from our lives. We need to have circumcised hearts too, see Romans 2:29
For the LORD your God is God of gods and Lord of lords, the great, the mighty, and the awesome God, who is not partial and takes no bribe. Deuteronomy 10:17 (ESV)
God is the great and mighty sovereign, what is comforting is that in all his supreme power he is not partial and can not be bribed. As we can see in the next verse Gods love extends to all people.
Not that we are sufficient in ourselves to claim anything as coming from us, but our sufficiency is from God, who has made us sufficient to be ministers of a new covenant, not of the letter but of the Spirit. For the letter kills, but the Spirit gives life. 2 Corinthians 3:5–6 (ESV)
We thank God for the new covenant we have in Jesus, the new covenant is better than the old one because we have the power of the Holy Spirit living inside us to enable us in our walk with God. The letter kills but the Spirit gives life should not be seen as the written Bible vs the Holy Spirit, in the context this is looking at the old covenant vs the new better covenant. Gods perfect law can only be kept through the Holy Spirit.
Contend, O LORD, with those who contend with me; fight against those who fight against me! Psalm 35:1 (ESV)
As 1 John 2:1 states we have an advocate (Jesus) who can contend for us against the enemy.
Let them be like chaff before the wind, with the angel of the LORD driving them away! Let their way be dark and slippery, with the angel of the LORD pursuing them! Psalm 35:5–6 (ESV)
We can pray in the same way that Gods Angels will go into battle on our behalf