(We shall limit ourselves to some brief extracts taken from his first Sermon for the Feast of Pentecost, on the six operations of the Holy Ghost. Cf. Collection of St Bernard's Sermons, vol. II, pp. 286 ff.)
1. The manifestation of the Holy Spirit:
If, therefore, we honour the festival days of the saints, with how much more reason should we honour his feast to whom the saints owe their very sanctity? . . . Today, then, is the Holy Spirit's feast day, because it was today that he, invisible in himself, appeared to the apostles in visible form. . . .
2. What we receive from him in order to turn us away from evil:
Accordingly, with the purpose of turning us away from evil, he operates three things within us, namely, compunction, supplication and remission. Repentance for sin is the beginning of our conversion to God, and this repentance, not our own spirit, but the Spirit of God, operates in us, as reason manifestly teaches and authority defines. Where is the man who, having come cold to the fire and warmed himself, can seriously doubt that the heat which he could not have enjoyed without the presence of the fire, has come to him really from the fire ? In the same way, therefore, he that was once cold in impiety and began afterwards to glow with the heat of a fervent repentance, ought to feel assured that another Spirit has descended upon him, and is reproving and condemning his own. For this we have the authority of Christ himself, who tells us in the Gospel, speaking of the Spirit whom the believers were about to receive, that: When he, the Paraclete, is come, he will reprove (D.V. convince) the world of sin (John 16. 8).
But what is the use of repentance unless it be accompanied with supplication for pardon? It is necessary, therefore, that the Spirit should operate this in us also, replenishing our minds with the peculiar sweetness of hope, so that we may ask in faith, nothing wavering (James 1. 6). Do you wish me to prove that this, likewise, is the work of the Holy Spirit? I say, then, that as long as he is absent, you can discover no such power of supplication in your own spirit. Besides, we have it on the authority of St Paul that he it is by whom we cry Abba, Father (Rom. 8. 15). And the same apostle assures us that the Spirit himself asketh for us with unspeakable groanings (ibid. 26). Both these operations of repentance and supplication the Holy Ghost accomplishes within our own hearts. But what does he do in the heart of the Father? As dwelling in us, he makes intercession for us; so, dwelling in the Father, he forgives with the Father: he is our Advocate with the Father in our hearts, he is our Lord in the Father's heart. . . . That you may know with full certainty that the remission of our sins is also an operation of the Holy Ghost hear what Christ once said to his apostles : Receive ye the Holy Ghost; whose sins you shall forgive, they are forgiven them (John 20. 22-23). So much for the operations whereby the Spirit helps our infirmity in the avoidance of evil.
3. What we receive from him to help us to do good:
Let us now consider what help to do good we receive from the `good Spirit' (Luke i i. 13). He admonishes us, he moves us, he instructs us. He admonishes our memory (John 14. 26), he moves our will, he instructs our reason: of which three faculties our souls entirely consist. He suggests that which is good to the memory in holy meditations, and thus banishes from our minds pusillanimity and sloth. Therefore, my brethren, as often as you become conscious of these promptings to good in your hearts, give glory to God and reverence the Holy Spirit, whose voice is sounding in your ears.
When therefore, the Spirit comes and thus takes complete possession of the soul, by admonishing and instructing and moving her; speaking ever in our thoughts, so that we can hear what the Lord God is saying to us, enlightening our understanding and inflaming our will: does it not seem to you, brethren, that the whole house of our soul has become filled 'with parted tongues, as it were, of fire' ? For, as I have said already, the soul is constituted entirely of memory, intellect, and will. The division of the tongues may be taken to represent the multiplicity of our thoughts, which in their very multiplicity can be said to resemble flames of fire, when the same light of truth and the same heat of charity appear manifest in all. Or perhaps I had better say that the filling of the whole house is reserved for the end, when, good measure and pressed down and shaken together and running over they shall give into your bosom (Luke 6. 38). But, when shall these things be ? Doubtless when the days of Pentecost shall have been accomplished. Happy they who have already entered upon the quinquagesima repose and the year of Jubilee. I speak of our brothers to whom The Spirit hath said that they may rest from their labours (Apoc. 14. 13).
There are two spiritual seasons which we have to celebrate. The one may be called quadragesima, the other quinquagesima; the one precedes the passion, the other follows the resurrection; the one is passed in compunction of heart and the lamentations of penance; the other in joy of spirit and the chanting of solemn alleluias. The one is the time of this present life; the other begins after death and is the period of the repose of the saints. But when this quinquagesima also comes to an end in the general resurrection and final judgement, 'the days of Pentecost being accomplished', then the Spirit shall descend in his fullness and the whole house shall be filled. For the whole earth shall be filled with his majesty (Ps. 71. 19), when not only shall the soul be purified, but the body too, `shall rise a spiritual body', if yet, according to the apostle's admonition, it has been sown in Christ while still an animal body (i Cor. 15. 43).