I have heard that the 10th rank of Angels will be monastics.
However, someone told me it will be monastics and us.
Would anyone know which one it is and which spiritual father has said this?
Great answers above!
I have read before that monastics are as Angels, according to their kindred spirit, humility, obedience, and servitude. Not, however, that they become Angels. They remain always ontologically distinct, according to their nature.
But how cool if God replaced that rank of angels who fell from the heavens, and gave it to men who were more like Angels than them, monastics who lived in angelic hope, virtue and obedience. Perhaps the faith and service of the monastics play an important role in God's plans for man's salvation, and perhaps they will stand next to the Angels in the Kingdom of Heaven.
While these monastic 'angels' share ultimately in the same glory and worship of God together with all the heavenly Angels, their respective ontological being and personhood remain distinct. And this distinction is one which makes no judgement on glory or love, but rather points to the glory and love of the Father in Heaven, and the grace and communion of the Holy Trinity.