1 Samuel 1

2 Having multiple wives at this time was often accepted even though God's design was one woman for one man.
3 Even so, Elkanah was a devout worshiper of God when most of those around him were not.
4 Elkanah offered a fellowship offering to show his thankfulness to God. The entire family ate this kind of sacrifice (Lev 7:11-18).
5 Elkanah loved Hannah, but she had no children. During these times it was considered a disgrace and a curse not to have children. This may have led to a situation like that with Abraham and Sarah where Abraham had children by Sarah's slave woman so that Sarah could adopt the first child and no longer be disgraced (Gen 16:1-2).
6 But as with Sarah and Hagar, the wife with children exalted herself above her who did not. This was a powerful weapon for the less-loved rival wife who happened to be more "productive" (Gen 16:4). Another example of rival wives is Jacob's family (Gen 29:30-30:25).
7 The fellowship offering was supposed to be a time of reconciliation between man and God, and between people. Despite this, Peninnah used it for an opportunity to gloat over her own children and make Hannah miserable. Such humiliation made it difficult for Hannah to participate in the festival with a joyful heart.
8 Elkanah is trying to console his wife by confirming his great love for her, but Hannah was not comforted.

Ten sons would have been an enormous family and would have undoubtedly brought great honor to the mother who bore them.

11 It is difficult to get away from the idea that Hannah is trying to make a bargain with God. She is so desperate for a son that she would even give him up immediately to God if she could just have one. She vowed that this son would be a Nazirite from birth and would be completely set apart for God's work.
13 Hannah must have been in great distress to be mistaken for being drunk. Perhaps Eli had never seen anyone come before God with such earnest prayer.
17 After her explanation Eli realized his mistaken accusation and then blesses her because of her earnest prayer.
18 Hannah took the priest at his word. Her faith in God now lifted her spirits and she was able to participate in the remainder of the festival with joy.
19 The implication is that this was a miraculous birth that God caused to happen.
20 Samuel means, "name of God," according to the Ryrie Study Bible footnote.
22 Samuel was born just before the annual festival. Hannah is not selfishly keeping the child to herself, but it is proper to make sure that the baby is weaned before giving him to someone else to feed and care for. We see in verse 24 that she immediately carries out her vow once Samuel is eating solid foods.
23 Elkanah's words seem a little confusing. Perhaps he is saying, "God has given us the child, and in due time He will bring Hannah's vow to completion."
24 Wycliffe uses an external source to imply that Samuel may have been upwards of three years old when he was weaned. But the flow of the text would only imply that Hannah remained at home during the one festival and that this sacrifice was given before the next festival.

Apparently there is a difference among the original texts here. One reads, "three-year-old bull," while another reads, "three [one-] year-old bulls." Even though the former is used by NAS, it would be unusual since nowhere else in the Bible (that I can remember) is any bull over one year old used in a sacrifice. If the latter is the true translation then the additional bulls may have been used as a gift and a thank offering as described by Wycliffe.

The rules for a Nazirite are given in Num 6:2-21. The initial offering is not described, but it can be implied by noting that a sin offering was required in Num 6:9 if his hair was defiled during the time of his vow. To be dedicated to God in the first place he would have had to make an appropriate sin offering.

26 Eli may not have remembered Hannah.
28 Hannah has fulfilled her vow. Eli may not have seen anything like this and was struck with wonder at this woman's great gift. His immediate response was to worship God.