1 Peter 2:9-11

but you are an elect race, a royal priesthood, a holy nation, a purchased people; that you should declare the perfections of him who has called you from darkness into his marvelous light:

1 John 1:7

But if we walk in the light, as he is in the light; we have fellowship with one another, and the blood of Jesus Christ the Son cleanses us from all sin.

1 John 2:8-11

On the other hand, I write to you a new commandment, which is true concerning him and concerning you. For the darkness is passing away, and the light, which is true, now shines.

Treasury of Scripture Knowledge

Summary

For ye were sometimes darkness, but now are ye light in the Lord: walk as children of light:

Bible References

Ye were

1 Peter 2:9
but you are an elect race, a royal priesthood, a holy nation, a purchased people; that you should declare the perfections of him who has called you from darkness into his marvelous light:
1 John 2:8
On the other hand, I write to you a new commandment, which is true concerning him and concerning you. For the darkness is passing away, and the light, which is true, now shines.