Musar zu Bamidbar 5:28

ואם לא נטמאה האשה וטהורה היא, "If the woman has not defiled herself, but is pure, she will remain unharmed and able to retain seed" (5,28). Why would the Torah have to add the words "she is pure," since this is obvious "if she had not defiled herself?" The deeper meaning is that if someone had defiled himself and subsequently purified himself through remorse and whatever purifying process prescribed, the Torah promises us that such "purity" is also subject to its blessing; repentance is such a great moral accomplishment that it turns erstwhile debits into merits (Yoma 86b).

לא תשא את שם ידו"ד אלהיך. The Rekanati describes anyone who swears a vain or false oath as קוצץ בנטיעות cutting planted trees, i.e. damaging G–d's universe. This is the reason the Torah used the expression לא תשא instead of לא תשבע. By using the expression תשא the idea is conveyed that the groom should not be separated from the bride, [the word is used as נישואים marriage. Ed.] When the Torah continues כי לא ינקה השם, "that G–d will not clear one who does so," this is a reference to another verse in which a person has been cleared, ונקתה, and the resulting union with her husband is fruitful (Numbers 5,28). He who separates will not be cleared, however. Thus far the Rekananti. I have already explained elsewhere how the word שבועה, oath, is derived from שבעה, seven, and is connected with the בנין the "structure" of the universe, something G–d created in seven days. You may read up about this in my treatise שבועות, פרק תורה אור, חלק תורה תמימה.

But at that very moment Israel declared, ‘We will do’ before ‘We will hear’ (Shemos 24:7) and all of them were shown to be righteous, as it is stated, “You are entirely beautiful, my beloved, and there is no flaw in you” (Shir HaShirim 4:7). And it is also said of them, “Who can find a woman of valor” (Mishlei 31:10) and, “A woman of valor is a crown for her husband” (Mishlei 12:4). Therefore the Zohar (ibid., 96b) refers to the flour offering of Shavuos as a “jealousy offering” (Bamidbar 5:18). It is also called a “new flour offering” (Vayikra 23:16) because Israel was as if created anew the day the Torah was given. Thus they resembled a straying wife who is discovered to be unsullied, of whom it is stated, “She shall be exonerated and seed shall be sown and she shall be pure” (Bamidbar 5:28). And so did Israel become pure after they brought the Shavuos offering.