Romans 8:17

‘And if children, then heirs, heirs of God, and joint-heirs with Christ, if so be that we suffer with him, that we may also be glorified with him.'

Furthermore the Spirit bears witness to even more. He bears witness to the fact that as children we are heirs, heirs of God, and joint-heirs with Christ. He brings out that we are to share with Christ in all the gifts and glory of the Father. Thus will we receive the inheritance promised to Abraham (Romans 4:13; Genesis 12:3 ff. and often), an inheritance that will be received, not in this earth, but in the new Heaven and the new earth (Hebrews 11:10; 2 Peter 3:13). But Paul then enters a caveat. Such a privilege can only be ours if we share in His suffering. Those who would share the glory must share the cross. For it is the destiny of believers to experience suffering on the way to glory. ‘If we die with Him we will also live with Him, if we suffer with Him we will also reign with Him' (2 Timothy 2:11). It was not that Paul doubted the Roman Christians (any more than he distrusted Timothy). It was rather that he wanted them to be prepared for what might come (and soon did come).