She made a vow in 1 Sam 1:11
Numbers 15:8-9
And when you offer a bull as a burnt offering or sacrifice, to fulfil
a vow or for peace offerings to the Lord, then one shall offer with
the bull a grain offering of three tenths of an ephah of fine flour,
mixed with half a hin of oil.
so she fulfilled it in 1 Sam 1:24 but brought little bit more
actual translation not three years old bull but three bulls
For over a century most commentators have read פר משׁלשׁ (pr mšlš, “a
three-year-old bull”) with the LXX (cf. also Gen 15:9) instead of the
MT’s פמ[י]ם שׁלשׁה (pr[y]m šlšh, “three bulls”), assuming that the m
on pr[y]m was misplaced. The LXX reading has now been confirmed by
4QSama: [pr bn] bqr mšlš. For parallel usage at Nuzi, where (as here
and in Gen 15:9) the animal’s age specifies maturity for purposes of
sacrifice, see E.A. Speiser, “The Nuzi Tablets Solve a Puzzle in the
Books of Samuel,” BASOR 72 (1938): 15–17.
http://www.jstor.org/stable/3218866?seq=1#page_scan_tab_contents
https://books.google.co.uk/books?id=Ti3E1LbGdOoC&lpg=PA49&ots=Iyfdzi7iV5&dq=The%20Nuzi%20Tablets%20Solve%20a%20Puzzle%20in%20the%20Books%20of%20Samuel&pg=PA49#v=onepage&q=The%20Nuzi%20Tablets%20Solve%20a%20Puzzle%20in%20the%20Books%20of%20Samuel&f=false
Wenham, for example, in commenting on Hannah’s offering, suggests that
“one bull was for the burnt offering, one for the purification
offering that was expected after childbirth (Lev. 12), and the third
for the peace offering, in payment of her vow.” (G. J. Wenham, The
Book of Leviticus (NICOT; Grand Rapids: Eerdmans, 1979), 79 n.12.
Other defenders of the Masoretic text’s reading include R. Ratner,
“Three Bulls or One? A Reappraisal of 1 Samuel 1,24,” Bib 68 (1987):
98–102; followed by R. Bergen, 1, 2 Samuel (NAC; Nashville: Broadman &
Holman, 1996), 73. Among modern translations, JPS also follows “three
bulls.”)
1:24 When Samuel was weaned, Hannah was prepared to fulfill her vow. Three years is mentioned as the usual period of lactation among Hebrew women in 2 Macc 7:27, but the rabbis make the time a year less.26 She took the boy with her to Shiloh. Elkanah is not mentioned, but it is clear from 2:11 that he accompanied Hannah.
A great feast normally was held in conjunction with the weaning of a child (Gen 21:8), but in the house of Elkanah the participants must have had mixed emotions. Some object that a child possibly as young as two would have been a great burden to Eli. There were, however, women engaged in tabernacle service (1 Sam 2:22). One of them might have acted as surrogate mother to the lad in his most tender years. It was important that he be dedicated to the Lord as soon as possible. The earliest impressions of his youth were to be those of the sanctuary (Kirkpatrick, 1:50).
Along with the child, Hannah took to Shiloh materials for sacrifice. First, she took a three-year-old bull, lit., “three bulls.” The NIV has chosen to follow the LXX in postulating one bull.27 Probably the one bull in v. 25 was the special burnt offering used to accompany the dedication of Samuel to the Lord, while the other two bulls were for Elkanah’s usual yearly sacrifice consisting of a burnt offering and a thank offering.28 The choice of bulls when smaller animals would have sufficed (Lev 12:6) is indicative of the gratitude of both Hannah and Elkanah (Baldwin, 54). Second, she took an ephah (½ bushel) of flour. Three tenths of an ephah of flour were to be offered with each bullock (Num 15:9). Third, she took a skin of wine for a special sacrifice. Liquids were transported in animal skins which had been specially prepared for that purpose. A wineskin would hold a considerable quantity of wine, more than enough to satisfy the prescribed drink-offering with each bull of half an hin of wine (Num 15:10) which would be equivalent to about three pints. The house of the Lord here is equivalent to the “Lord’s temple” in v. 9. See comments there.
The NIV has rearranged the word order of v. 24 and thereby obscured an important point. The words young as he was (lit., “and the child was a child”)29 actually stand last in the verse. The phrase contains a play on the word נַעַר (na˓ar) which can mean “child” or “servant.” Hannah brought the child to Shiloh and the child (hanna˓ar) was/became a na˓ar, i.e., he took up his role as a servant to the priests once he got to Shiloh. This play on words underscores (1) the exact compliance of Hannah with the terms of her vow; and (2) the commencement of Samuel’s tabernacle duties at the tenderest of ages. 1 & 2 Samuel. The College Press NIV commentary. (48).
that's all i could find