6 This interpretation, also, brethren, displeases me not, since it does not militate against the faith. Yet I cannot but remark that it is not only said, “As one taken away from milk, such may be my soul's reward;” but with this addition, “As one taken away from milk when upon his mother's breast, such may be my soul's reward.” Here there is somewhat that induces me to consider it a curse. For it is not an infant, but a grown child that is taken away from milk; he who is weak in his earliest infancy, which is his true infancy, is upon his mother's breast: if perchance he has been taken away from the milk, he perishes.
It is not without a reason then that it is added, “Upon his mother's breast.” For all may be weaned by growing. He who grows, and is thus taken away from milk, it is good for him; but hurtful for him who is still upon his mother's breast. We must therefore beware, my brethren, and be fearful, lest any one be taken away from milk before his time....Let him not therefore wish to lift up his soul, when perchance he is not fit to take meat, but let him fulfil the commandments of humility.
He has wherein he may exercise himself: let him believe in Christ, that he may understand Christ. He cannot see the Word, he cannot understand the equality of the Word with the Father, he cannot as yet see the equality of the Holy Spirit with the Father and the Word; let him believe this, and suck it. He is safe, because, when he has grown, he will eat, which he could not do before he grew by sucking: and he has a point to stretch towards. Seek not out the things that are too hard for you, and search not the things that are above your strength; that is, things which you are not as yet fit to understand.
And what am I to do? You reply. Shall I remain thus? “But what things the Lord has commanded you, think thereupon always.” What has the Lord commanded you? Do works of mercy, part not with the peace of the Church, place not your trust in man, tempt not God by longing for miracles....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)