St. Augustine of Hippo (354-430) in his treatise De bono coniugale (On the Good of Marriage) shows how the same virtue is at the heart of both marriage and celibacy.
He begins by affirming that each human person “is a part of the human race, and human nature is something social,” and that “the first natural bond of human society is man and wife.” He adds: “Nor did God create these each by himself, and join them together as alien by birth: but He created the one out of the other, setting a sign also of the power of the union in the side, whence she was drawn, was formed. For they are joined one to another side by side, who walk together, and look together whither they walk.” (1)
Christ confirmed the good of marriage “not only in that He forbade to put away a wife save because of fornication (Matt 19:9), but also in that He came by invitation to a marriage (John 2:2).” (3) Hence, St. Augustine declares: “Marriage, I say, is a good, and may be, by sound reason, defended against all calumnies.” (24) But Christ also confirmed the good of voluntary celibacy, for He says of those who refrain from marriage: “Whoso can receive, let him receive” (Matt 19:12).
St. Augustine writes: “Continence is a virtue, not of the body, but of the soul. But the virtues of the soul are sometimes shown in work, sometimes lie hid in habit, as the virtue of martyrdom shone forth and appeared by enduring sufferings; but how many are there of the same virtue of mind, unto whom trial is wanting?” (25) He offers St. John the Apostle and Abraham as examples to illustrate this point. Concerning the merits of how they lived out their lives, he asserts: “There is not unequal desert of continence in John who made no trial of marriage, and in Abraham, who begat sons. For both the celibate of the one, and the marriage estate of the other, did service as soldiers to Christ, as times were allotted; but John had continence in work also, but Abraham in habit alone.” (26)
Finally, lest anyone presume that the married state is necessarily easier than the celibate state, St. Augustine remarks: “Many indeed with more ease practise abstinence, so as not to use, than practise temperance, so as to use well.” (25)
Quotations from A Select Library of the Nicene and Post-Nicene Fathers of the Christian Church, Vol. III, ed. Philip Schaff (Edinburgh: T&T Clark, 1886).