The phrase "in the Spirit" occurs many many times in the NT such as: 1 Tim 3:16, Luke 1:17, 2:27, Acts 18:25, Eph 1:13, 8:18, Rom 8:4, 1 Thess 1:5, etc. Thus, NT writers are said to:
- "pray in the Spirit" (Eph 6:18)
- "led by the Spirit" (Luke 2:27, 4:1)
- "fervent in the Spirit" (Acts 18:25)
- "sealed in the Spirit" (Eph 1:13)
- "walk in the Spirit" (Rom 8:4)
- "rejoice in the Spirit" (Luke 10:21)
- "live by/in the Spirit" (Gal 5:25, Rom 7:6, 1Cor 5:5)
- "worship in Spirit" (John 4:23, Phil 3:3)
- "made alive in the Spirit" (1 Peter 3:18)
- "united in the Spirit" (Eph 4:3)
... and so forth. Thus, to be "in the Spirit" in the many variations that exist in the NT is to be motivated and act according to the impulses and leading of the Holy Spirit according to the divine will of heaven. This may mean saying, doing or receiving messages from the Spirit. This is consistent with teaching in John 16:13 -
However, when the Spirit of truth comes, He will guide you into all
truth. For He will not speak on His own, but He will speak what He
hears, and He will declare to you what is to come.