Paul here exhorts the Ephesian Christians to pray ‘in the Spirit’ at all times. Therefore, he is not suggesting a special kind of prayer that is limited to a few Christians who have attained an advanced standing as believers; rather he is referring to the only kind of true prayer there is. Any other kind of prayer is not Christian prayer.
To be ‘in the Spirit’ is a Pauline description of what it means to be a Christian. He writes in Romans 8:9: ‘You, however, are not in the flesh but in the Spirit, if in fact the Spirit of God dwells in you. Anyone who does not have the Spirit of Christ does not belong to him.’ In that verse Paul states that there are only two kinds of people on the earth, those in the flesh and those in the Spirit.
Elsewhere Paul mentions several Christian outlooks that only exist because believers are ‘in the Spirit’. The attitude of love is depicted in Colossians 1:7-8: Epaphras ‘is a faithful minister of Christ on your behalf and has made known to us your love in the Spirit’. The practice of Christian fellowship is described in Philippians 2:1: ‘So if there is any encouragement in Christ, any comfort from love, any participation in the Spirit, any affection and sympathy, complete my joy by being of the same mind, having the same love, being in full accord and of one mind.’ In Galatians 5 Paul twice uses the phrase ‘walk in the Spirit’: in verse 16 he encourages his readers when he writes: ‘Walk in the Spirit, and ye shall not fulfil the lust of the flesh’; in verse 25 he concludes his contrast between the works of the flesh and the fruit of the Spirit by saying, ‘If we live in the Spirit, let us also walk in the Spirit.’
Paul has already referred in this letter to various blessings connected to the presence of the Holy Spirit in believers. The Spirit is the mark of divine ownership, that they belong to God and are protected by him (Eph. 1:13). Connected to this is the fact that his presence is the guarantee to each believer that he or she will receive the promised inheritance (1:14). In the Spirit, all believers have access to the Father (2:18). In or by the Spirit, God dwells in his church (2:22). The Spirit has greatly privileged New Testament believers by revealing to them aspects of truth that was not revealed so fully to Old Testament believers (3:5). His indwelling gives to believers the power or capability to know experientially the love of Christ (3:16ff.). He is the means of unity among Christians of different racial and social backgrounds (4:3-4). Sadly, it is possible for Christians to grieve him by their wilful sins (4:30). Instead of grieving him, believers should be controlled by him (5:18). He has also given them his word as the sword to use to defeat the attacking powers of darkness (6:17). It is clear that every Christian activity is performed in the Spirit.
Every Christian can and must be filled by the Spirit, can and must walk in the Spirit, and can and must pray in the Spirit.