Grace and Law should fit together as Jesus said. We shouldn't throw out either one. It was a huge part of the OT and it's still the mainstay of the NT.
GRACE IN THE OT
Grace has ALWAYS been a part of this ETERNAL covenant that started with Abraham, passed down to his descendants through Moses, and is ratified in it's final form through Jesus Christ. There's too many scriptures on God's grace in the OT to list them all, but note the book of Psalms is the Songbook for the Israelites. It's filled with words about God's mercy, faithfulness, loving kindness, etc.
Psalms 32:2, Psalms 51:10, Psalms 109:26, 1 Chronicles 16:34, Ezra 9:9, Nehemiah 9:31-32, Nehemiah 13:22, Psalms 5:7, Psalms 23:6, Psalms 33:18, Psalms 33:22, Psalms 36:5, Psalms 52:8, Psalms 59:17, Psalms 86:15, Psalms 98:3, Psalms 100:5, Psalms 105:8, Psalms 136, Proverbs 28:13, Isaiah 14:1, Isaiah 54:8-10, Isaiah 55:7, Jeremiah 31:20, Ezekiel 39:25, Daniel 9:9, Hosea 1:7-8, Micah 7:18-20, Zechariah 1:16, Zechariah 10:6
GRACE AND TRUTH OT AND NT
Please note how GRACE and TRUTH have also been a huge part of the OC. John 1:14, John 1:17, Colossians 1:6, 2 John 1:3, Genesis 24:27, 2 Samuel 15:20, Proverbs 3:3, Proverbs 16:6, Micah 7:20