Naso - R'vi'i
The Sotah, The Nazir and the Priestly Blessings
G-d gave Moshe instructions for a woman suspected of adultery (sotah). This is a case where a man has suspicions, he expresses them to his wife, then she puts herself in a compromising situation.
The husband brings the wife to the kohein with a flour offering. Since it is a "jealousy offering," oil and frankincense are not used. The kohein takes water from the basin and puts it in a previously-unused clay bowl, along with some dust from the floor of the Mishkan. The kohein uncovers the woman's hair (the Chumash taking for granted that a married woman's hair is covered) and places her hands on the offering, while he holds the "bitter waters."
The kohein administers an oath to the woman to the effect that she has not been unfaithful to her husband. If she is innocent, the waters will not harm her, but if she's guilty as charged, her reproductive organs will be the death of her. (This penalty is described in a colorful fashion as her "thigh" - a euphemism - falling off and her womb swelling.) The woman replies, "Amen, amen."
The kohein writes the oath and its penalties in a scroll, which he then erases in the waters (even though the text contains the Name of G-d). He causes the woman to drink the waters, then he takes the offering from the woman. He waves it and scoops out three fingers full, which he burns on the altar.
If the woman is guilty, she will perish in the described manner. (Not necessarily immediately - it might take up to three years based on her merits - see Mishna Sotah 3:4.) If she is innocent, she will conceive and bear a child for her trouble.
It should be noted that for most of the process, the woman could refuse or back out (basically because she knew she was guilty and didn’t want to suffer the penalty). If the woman opted out, she would be divorced without being paid the value of her kesubah (marital contract). The point of no return was once the scroll was erased. At that point she could confess and stop the process, but if she merely refused to continue, she would be compelled to drink. (See Mishna Sotah 3:3.)
Next, G-d told Moshe the process for the Nazirite. (We'll stick with the Hebrew term, which is simply Nazir.)
A person who vows to be a Nazir must separate from all wine and grape products for a specified period (the norm is 30 days). The Nazir may not cut his hair or become ritually impure through the dead - not even for his own parents or siblings! He is consecrated to G-d for the duration of his vow.
If someone spontaneously dies in the vicinity of the Nazir, making him unclean, he must purify himself on the seventh day, shaving his head. (We shall see the process of purification for corpse uncleanliness in parshas Chukas, chapter 19). On the eighth day, he must bring a sacrifice of two birds, one as a sin offering and one as a burnt offering. After that, he starts his period as a Nazir all over again and brings a sheep as a guilt offering.
When his term as a Nazir is concluded, the person brings a sacrifice of a male sheep for a burnt offering, a female sheep for a sin offering and a ram for a peace offering. (What sin did the Nazir do that he is required to bring the korban chatas? Self-deprivation of things that are permitted. See Talmud Nazir 19a. On the other hand, Nachmanides finds the Nazir’s actions meritorious and says the sin is returning to a life of temporal pleasures – see Ramban on 6:14.)
While the kohein presents the Nazir's offerings, the Nazir shaves his own head and throws the hair on the fire. The kohein would place the cooked leg of the ram, a loaf and a matzah in the Nazir's hands and lead him in the waving motion. (These were among the portions given to the kohein, as per Exodus chapter 29.) After this, the Nazir can drink wine again.
Next, G-d gave Moshe the text that the kohanim should use to bless the people. These three blessings (that G-d should bless and watch the Jews, that He should shine His face on them and give them His grace, and that He should turn His attention to them and grant them peace) are still used today.