Sirach 23:9
Ben Sira, Ecclesiasticus7 Listen, my children, to instruction concerning the mouth; the one who observes it will never be caught. 8 Sinners are overtaken through their lips; by them the reviler and the arrogant are tripped up. 9 Do not accustom your mouth to oaths, nor habitually utter the name of the Holy One; 10 for as a servant who is constantly under scrutiny will not lack bruises, so also the person who always swears and utters the Name will never be cleansed from sin. 11 The one who swears many oaths is full of iniquity, and the scourge will not leave his house. If he swears in error, his sin remains on him, and if he disregards it, he sins doubly; if he swears a false oath, he will not be justified, for his house will be filled with calamities.
John Chrysostom Homily 10 on Acts 1:9
Well, then, let us speak to you today from the Old Testament. What does it tell us? Accustom not your mouth to swearing; neither use yourself to the naming of the Holy One. And why? For as a servant that is continually beaten shall not be without a blue mark, so he that swears. See the discernment of this wise man. He did not say, Accustom not to swearing your mind, but your mouth; because being altogether an affair of the mouth, thus it is easily remedied. For at last it becomes a habit without intention; as for instance, there are many who entering the public baths, as soon as they have passed the threshold, cross Hom. in themselves (σφραγίζονται). This the hand has got to do, without any one's bidding, by force of habit. Again, at the lighting of a candle, often when the mind is intent on something else, the hand makes the sign. In the same way also the mouth, without concurrence of the mind, articulates the word, from mere habit, and the whole affair is in the tongue.
Notes and References
"... The golden age of Greek patristic literature, that is, the fourth and fifth centuries, are no exception as far as the popularity of Sirach. Besides John Chrysostom, nearly all of the most prominent authors of this period cite from Sirach, including, inter alia, Clement of Alexandria, Ambrose, and Augustine. Clement of Alexandria even believed that Sirach had influenced the Greek philosopher Heraclitus (Stromata 2:5). Sirach was also popular with authors such as Tertullian, Origen and Cyprian. Jerome, however, rejected the canonical status of Sirach. The first full commentary on Sirach was only completed in the ninth century by Rabanus Maurus. The citations in John’s homilies are often sporadic proof-texts. But what is interesting is the constant repetition of certain citations, citations that seem to have remained in John’s memory. The homilies on the books of the New Testament come in the guise of a sermonic commentary, with verse-by-verse expositions. But inside these expositions one finds many other citations which were probably quoted from memory and not necessarily from a text. It is therefore problematic to speculate from which text or version a citation originates, since John probably memorized many Sirachic proverbs during his monastic retreat or ministerial period. This obviously does not rule out the possibility that John probably had a written text at his disposal (which he may have read for study and devotion). Some proverbs are cited or alluded to more often than others. The more popular citations, which occur frequently in the homilies, are Sirach 1:22; 5:6; and 18:16-17. Other citations occurring more than once include Sirach 2:4; 3:30; 4:8; 9:9, 13, 15; 10:9, 12-13; 11:3; 13:15; 15:9; 16:3, 12; 18:30; 19:10-11; 21:2; 23:10, 17; 28:3; and 34:23. There are a total of 65 individual verses cited from Sirach in John’s New Testament homilies, only slightly fewer than the 77 verses cited from Proverbs ..."
de Wet, Chris John Chrysostom's Use of the Book of Sirach in his Homilies on the New Testament (pp. 1-6) University of Pretoria, 2010