That which is born. That (Neuter) which has been begotten. Note the difference between this Perfect here and in John 3:8 and the Aorists in verses: John 3:3; John 3:3; John 3:4; John 3:5; John 3:7.
flesh. See note on John 1:13.
the Spirit: the Holy Spirit (with Art.) See App-101.
is spirit. This is. fundamental law, both in nature and grace.