Good morning! This verse is the second half of a sentence that starts in verse five. It says, "Not that we are sufficient of ourselves to think of anything as being from ourselves, but our sufficiency is from God..." So, the context is our trust is in God to carry out life, not our own righteous deeds.
The letter gave ordinances of righteousness to be carried out. Many of the leaders, even in Jesus' day, were trusting in their ability to keep the law. They trusted in their own abilities and righteous deeds according to the law and their flesh. But it is the Spirit who gives life.
The letter brought death and was only a mirror to show us our need for a Savior. It made no one righteous, but allowed God to death with us in our sin. It atoned, or covered/buried our sins. But the Spirit is new the letter of the law that brings life through redemption which removed our sin entirely.
At the giving of the law in Moses' day, those who refused to be on the side of the Lord were destroyed and it was three thousand in number. On the Day of Pentecost, the disciples were filled with the Holy Spirit and after Peter preached, three thousand were added to the church. The letter kills, but the Spirit gives life! Choose to live by the Spirit and you will have eternal life and learn how to make each day a great day!
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