‘Now the Lord is the spirit, and where the Spirit of the Lord is, there is liberty.'
We must probably see this as an explanation of Whom ‘the Lord' is in 2 Corinthians 3:16. If ‘the Lord' there refers back to the Lord in the Old Testament because it has Jews in mind, then this is simply pointing out that the Spirit of the Lord is the Lord manifested in power. The Lord is the Spirit, and where the Spirit of the Lord is, there is freedom, freedom from the Law, freedom from condemnation. Turning to the Lord truly results in such freedom.
The suggestion that it simply means the Holy Spirit as bearing the title ‘Lord' must be seen as doubtful because it would be unusual to speak of ‘turning to the Spirit' as would be implied in 2 Corinthians 3:16. That would be using an idea which is unparalleled elsewhere. The Spirit always points away from Himself. Furthermore the reference to the ‘Spirit of the Lord' in the second part of this verse also suggests that there too the Lord is not the Spirit either. He cannot be the Spirit of Himself. In fact taking ‘Spirit of the Lord' to signify the Spirit of Yahweh, ‘the Lord' in that phrase here means the God of the Old Testament.
But if it did mean ‘the Lord is the (Holy) Spirit' then it would suggest that it was Paul's intentions to indicate that Jesus is the Lord (2 Corinthians 3:16), and the Spirit is the Lord (2 Corinthians 3:17 a), although also still being the Spirit of Yahweh (the Lord) (2 Corinthians 3:17 b), Who is Lord over all, a clear statement of the triunity of ‘the Lord'.
However, the probability in the context of Corinthians must be that the Lord in 2 Corinthians 3:16 refers to Jesus Christ. And there is no difficulty in the phrase ‘the Spirit of the Lord' then because Paul would certainly have no difficulty in aligning Jesus Christ with the Lord of the Old Testament. He calls Him ‘the Lord, Jesus Christ' and elsewhere declares that ‘Jesus is Lord', bearing the name that is above every name (Romans 10:9; Philippians 2:8-11). Thus it is the equivalent of the Spirit of Christ (Romans 10:9). But if that is so what could the first part of this verse mean.
How then is ‘the Lord that spirit'? One possible explanation in this case is that we should use a small ‘s' and see ‘the Lord is that spirit' as being intended as an explanation, tying together the reference to the Lord in 2 Corinthians 3:16, where His function is to give light and life, with the references to the spirit in 2 Corinthians 3:6 b and 6c, where the idea is similar, to show that the ‘spirit' referred to there is not intended to refer directly to the Spirit of the living God of 2 Corinthians 3:3 but to ‘the spirit of Jesus', this being seen in terms of the ‘life-giving spirit' of 1 Corinthians 15:45; (‘spirit in 2 Corinthians 3:6 b is without the article, possibly to distinguish it from the reference in 2 Corinthians 3:3, so that the article in 6c and here in 17 could be referring back to 2 Corinthians 3:6 b). Compare also 1 Corinthians 6:17.
Then Paul is saying, ‘the Lord in 2 Corinthians 3:16 is the essence of the ‘spirit' which is in contrast to the ‘letter', the spirit that reveals, the spirit that gives life, the life-giving spirit, and it is Jesus Who is the life-giving spirit, (1 Corinthians 15:45) Who works by means of the Spirit of the Lord', Who can elsewhere be described as the Spirit of Christ (Romans 10:9). Compare John 5:22; John 5:26 where ‘the Son makes alive whom He will' and ‘has life in Himself'. He is the life-giving spirit. This would not have the same difficulties for Paul's readers as it does to us, for they would not in their minds have crystallised the persona of God as much as we do. They were happy to see God as Spirit (John 4:24), Jesus as life-giving Spirit (1 Corinthians 15:45), and the Holy Spirit as Spirit.
Alternately it may simply mean that the Lord reveals His truth through the Spirit. The Lord is manifested by the Spirit.
The final implication is that again through Him there is freedom from the Law as interpreted in the Synagogue, and from its condemnation, from the law of sin and death (Romans 8:2). They are no longer legally bound by its requirements, they have escaped the spirit of bondage and the fear it produces (Romans 8:15 a). They are instead free and at liberty, they are sons who observe the family rules (Romans 8:15 b). They are under the law to Christ, responsible to obey Him (1 Corinthians 9:21). But they are not under the condemnation of the Law.
All this is not, of course, to deny the clear implication of the closeness of the Lord with the Holy Spirit, as the second half of 2 Corinthians 3:17 reveals, for such closeness can be paralleled in John 14:17-18; John 14:20; John 14:23 and Romans 8:9. Whatever view we take it clearly indicates the close relationship between the Lord and the Spirit.