Irenaeus of Lyons:
To save us from forfeiting life by losing the Spirit who possesses us, and to exhort us to share in the Spirit, the Apostle declares that it is impossible for flesh and blood to gain possession of the kingdom of God.
In other words: Do not deceive yourselves, for if the Word of God and the Spirit of the Father do not dwell in you, and you lead a life of vanity and carelessness, as though you were merely flesh and blood, you cannot obtain the kingdom of God.
He says this to prevent us from indulging our physical nature and spurning the grafting of the spirit, for when you were a wild olive, he says, you were grafted into the cultivated olive and came to share that olive’s rich sap.

