John Owen claimed that the mediatorial life of Christ in heaven ‘is not so considered nor so applied as it ought to be’; and again, ‘the darkness of our faith herein is the cause of all our disconsolations and most of our weakness in obedience.’

Owen adds,

‘Most men have only general and confused notions and apprehensions of the present state of Christ with respect unto the church.’

Yet:

‘This assumption of our Lord Jesus Christ into glory, or his glorious reception in heaven, with his state and condition therein, is a principle article of the faith of the church – the great foundation of its hope and consolation in the world…He leads not in heaven a life of mere glory, majesty and blessedness, but a life of office, love and care also. He lives as Mediator of the Church; as the King, Priest and Prophet thereof. Herein do our present safety and our future eternal salvation depend.’

Because Christ ascended:-

1. His (and our) humanity is affirmed.  ‘In the incarnation, God entered into human existence. In the Ascension, that humanity is taken up into the presence of God. We have a High Priest interceding for us who is not unable to sympathise with our challenges, dilemmas, suffering and weakness (Heb 4.15–16).’ (Ian Paul)
2. We worship him as reigning Lord.  Following Jesus’ own interpretation of Psa 110:1,4, (see Mk 12:35-37) we recognise his place as enthroned at God’s right hand as co-ruler, Rom 8:34; Heb 10:12f.  He is both ‘Lord’ and ‘Christ’, Acts 1:9.
3. We know that his atoning work is complete and final.  See Heb 10:11-14. This work rests on these four pillars – incarnation, crucifixion, resurrection, and ascension. And ascension confirms and crowns the rest: it is the sign that his humiliation and death were not in faith; nay, that they were gloriously triumphant. All that now remains in respect of his work of salvation is the final subjection of his enemies, and the establishment of the kingdom of God, 1 Cor 15:24-26.
4. We may approach God with confidence.  See Rom 8:34; Heb 5:9–10; 7:25; cf. Acts 4:12.  As advocate, he has the ear of the Father and intercedes for us, Heb 7:25. As high priest, standing within heaven’s courts, he helps those who are tempted, Heb 6:19–20).  Jesus can aid believers tempted to sin or apostatize (Heb 4:14–16).  Remember that Christ in his ascension has retained his human nature, and so is able to represent us with complete sympathy and understanding, Heb 9:24. ‘Christ’s intercession in heaven is a kind and powerful remembrance of his people, and of all their concerns, managed with state and majesty; not as a suppliant at the footstool, but as a crowned prince on the throne, at the right hand of the Father’ (Traill).
5. We have a divine benefactor. ‘He not only pleads our cause, presents our petitions, and secures our pardon, but he bestows our blessings. In ancient times, when warriors returned home from their conquests they led their captives with them and distributed largesse to their people, 1 Chron 16:1-3. And this is exactly what Paul says our Lord did, Eph 4:8-16.’ (J.O. Sanders).
6. We see a piercing of the barrier between earth and heaven.  Heaven is very definitely ‘open for business’ as a result of the ascension.  There a flurry of angelic activity, Acts 1:10–11; 5:19; 8:26; 10:3; 12:7–11, 23, together with the coming and continued activity of the Spirit, Acts 2:1–4; 4:8, 31; 6:10; 7:55; 8:17; 9:17; 10:44; 11:28; 13:2, 9, 52.  Other signals of this two-way traffic include exorcisms, Acts 5:16; 8:7; 16:16–18; 19:12, and sign and wonders in the front line of the battle, Acts 2:22, 43; 4:30; 5:12; 6:8; 14:3; 15:12.
7. We have a Saviour who can appear and act from heaven.  He appeared to Saul on the Damascus road, Acts 9:8.  Indeed, he counts persecution of believers as his own, Acts 9:5.  He speaks to Ananias to prepare to welcome Saul into the believing community, Acts 9:5.  He pours out the Spirit, Acts 2:33.  He heals Aeneas, Acts 9:34.  It is appropriate for believers to pray directly to him, Acts 9:14,21.
8. He sends his Spirit, as the earnest of the promised inheritance, Jn 7:37-39; 14:25; Acts 2:33. The descent of the Spirit was a direct consequence of the ascent of the Saviour, Acts 2:36. Hitherto, Jesus’s presence had been localised.  Now, he is everywhere present, sending his people with power to the end of the earth, Acts 1:8.
9. He will return ‘in the same way’, Acts 1:11.  ‘His return is never called the ‘second coming’ in the NT, because it is not paired with his ‘first coming’ (the Incarnation) but with the Ascension. As God has put all things under his feet, one day his authority de jury will be an authority de facto.’ (Ian Paul)
10. We have a pledge of our own future with him. ‘The dust of the earth is on the throne of the majesty on high’ (“Rabbi” Duncan). Where he is is now, we shall be hereafter, Jn 14:1-3. And the divine host is even now preparing a place for us.  Even now, he welcomes believers to himself, just as he welcomed Stephen, Acts 7:55f.  And when he returns, he will bring with him believers who have died to welcome those who are still alive, 1 Thess 4:14-17.
11. We have a great motive for heavenly-mindedness, Col 3:1-3; Eph 2:4-6.

Based in part on S. Walton, art. ‘Ascension of Jesus’ in DJG (2nd ed.)