‘Now he who is establishing (‘is confirming') us with you in Christ, and anointed us, is God, who also sealed us, and gave us the earnest of the Spirit in our hearts.'
And this is confirmed by the fact of Who has established them, and how He has done it. Let them recognise Who it is Who is ‘confirming', vindicating and authorising, he and his fellow-workers to them For he and his fellow-workers are, like the Corinthians themselves (‘with you'), God's men, firmly being established (being confirmed) in Christ, just as they are. And let the Corinthians remember that their own being established (being confirmed) in Christ owes much to Paul (1 Corinthians 1:6; 1 Corinthians 1:8). And it is this same faithful God who has anointed them all and has also sealed them, and given them the earnest of the Spirit in their hearts.
The idea behind ‘anointing' is essentially that of being set aside by God for His service. In the Old Testament kings, priests and prophets were all anointed. But it was only in certain specific cases that it resulted in the coming of the Spirit of God. Interestingly there is never any suggestion that priestly anointing resulted in the coming of the Spirit. That was for ‘the prophets' (Numbers 11:29). The two ideas were therefore not necessarily parallel. Anointing and the coming of the Spirit of God are two separate ideas, even if the second did sometimes follow the first, and with Christians will occur together.
So here the anointing is the indication of their all being separated to the service for God, and as having received His truth so that they are able to discern it truly (1 John 2:20). That is why they have an anointing. While their being sealed, and thus confirmed as God's, by reception of ‘the earnest of the Spirit' in their hearts, is confirmation that they belong to God, and are sealed as His personal possession. The earnest of the Holy Spirit is the guarantee of what is theirs and of what is to come.
An earnest is a ‘sample' of something that is promised, guaranteeing both the fact and the quality of what is to come. (When a trader had made a sale for future delivery he would often give a sample of the goods as evidence of the sale and as a guarantee of what the whole consignment would be like. It was called an ‘earnest'). So is the Spirit in their hearts God's guarantee that they are His, and a sample of what they will be and will receive in the consummation, when God is all in all.
It is made clear that these blessings are elsewhere received by all who become Christians. An anointing which makes sure to them the truth is described in 1 John 2:20; 1 John 2:27; the sealing is described in Ephesians 1:13; Ephesians 4:30 as signifying the presence of the Holy Spirit of promise and the guarantee of their partaking in the day of redemption, and the earnest of the Spirit is described as the guarantee of our inheritance until the redemption of God's own possession (Ephesians 1:14).
So Paul is here linking he and his fellow-workers with the Corinthian Christians as fellow participants in the grace of God. They are all one in being set apart by Him and in being partakers in the sealing by, and work of, the Holy Spirit (compare 1 Corinthians 12:13). Let there therefore be no more division.
Some note here the trinitarian element which so constantly appears in Paul (compare 1 Corinthians 12:4-6). The work of the Godhead is carried forward by, in this case, the faithful God, ‘God's Son' and by the Holy Spirit. For we must not forget that the Son is ‘born of' (is of the same essential nature as) the Father (John 1:14) and the Spirit ‘proceeds' from the Father (John 15:26), is of His essence. Note in this verse that ‘God' is specifically revealed as faithful, and was not ‘yes' and ‘no', in precisely the way that was revealed in the actions of God's Son, which are thus seen as His actions. In all they do the two are one.
It should be noted, as against some, that none of these blessings are ever directly connected with baptism in the New Testament so that there are no grounds for linking them directly with baptism here, even though the later church, as it became more formal, would make the link. Clearly baptism would outwardly indicate those who had previously experienced these things, indeed in the early days would follow immediately after as an indication that they were Spirit endued. But in the early days the reception of the Spirit was rather indicated more visibly in the power and joy that came on them (Galatians 3:2; Galatians 3:5; Acts 13:52). In Acts this sometimes came before baptism, sometimes at baptism, and sometimes after baptism. But in all cases the Spirit had been at work first. Paul trusted in the word of the cross in power as the saving agent, not baptism (1 Corinthians 1:17-18).