I am reading about animal sacrifices among Hebrews. When
the people made vows to sacrifice, to whom did they make the vows?

These vows (oaths, promises) were made to God. This article should
answer your question. Let me know if it does:

Oaths, Swearing, and Vows, Truthfulness, and Lying
http://www.teachmegod.com/home69.htm

Regards;
tutuzdad-ga

Animal sacrifices were instituted by Jehovah [ God`s name][Psalm
83;18] to teach His "chosen" people about the value of appreciating
what He did for them [ rescued them from Egyptian slavery/ crossing
the Red Sea]. Over fifteen hundred years it lead them up to Jesus` day
when God himself supplied Jesus as a sacrifice for us. When Jesus
instituted the "New Covenant" he did away with the " Old Covenant"
that had include animal sacrifice. Although God is all powerful, He
showed us what He was prepared to do to earn the worship He is
entitled to. In a small way a bit like a potter makes an earthenware
vessel. If it is beautiful, praise will result, and also the potter
has the right to destroy the same vessel. The process is to free us
from the sins in herited from Adam, the first man. And we all know his
story.Genesis 2;17.

Nonsense. Sacrifice is almost as old as man himself (LONG before
Egyptian slavery and the crossing of the Red Sea). In Christian
theology the rite of sacrifice was instituted immediately after the
eviction from Eden as a means through which man could atone for his
sins and nothing more. By sacrificing his valuable stock (or his other
belongings) to God man took a measurable loss - a severe penalty. It
hurt him (both emotionally and financially) to lose an animal or
property and in this way man continually but temporarily "paid" his
fine - he atoned for his sins through the death of his animal or the
burning and destruction of his property for example. An example of
this is the first recorded "offering" when God favored Abel's
sacrifice over Cain's because Abel's sacrifice was greater (i.e., a
greater penalty; i.e. it hurt him worse; i.e. it showed a greater
level of atonement).

"Gen 4:3  And in process of time it came to pass, that Cain brought of
the fruit of the ground an offering unto the LORD.
Gen 4:4  And Abel, he also brought of the firstlings of his flock and
of the fat thereof. And the LORD had respect unto Abel and to his
offering:
Gen 4:5  But unto Cain and to his offering he had not respect. And
Cain was very wroth, and his countenance fell."

God NEVER intended for sacrfices to serve as an outward sign that He
was "earning" ANYTHING. There is no Christian Biblical record or
scripture in the Holy Bible to support this notion and to say that God
felt the need to prove Himself to man is just factually absurd.

tutuzdad-ga

Exodus 32:9 "I have seen these people," the LORD said to Moses, "and
they are a stiff-necked people. Now leave me alone so that my anger
may burn against them and that I may destroy them. Then I will make
you into a great nation."

But Moses sought the favor of the LORD his God. "O LORD ," he said,
"why should your anger burn against your people, whom you brought out
of Egypt with great power and a mighty hand? Why should the Egyptians
say, 'It was with evil intent that he brought them out, to kill them
in the mountains and to wipe them off the face of the earth'? Turn
from your fierce anger; relent and do not bring disaster on your
people.

I don't see the relevance in that but...whatever. God doesn't "earn"
or have to earn anything. What we recieve from God is GRACE and
"grace" is defined as "a favored gift". A gift is not something that
HAS to be paid for:

Eph 2:8  For by grace are ye saved through faith; and that not of
yourselves: it is the gift of God:
Eph 2:9  Not of works, lest any man should boast. 

Sacrifice was intended to atone for man's sins in the time that it was
practiced, and was not in ANY WAY intended to pay God for His good
works.

tutuzdad-ga

Dear Tutuz. I wont say nonsense, because I hope we are all searching
for the right way to please God. But Adam was a long time before the
days of Moses. Why I mentioned the escape from Egypt and the Red Sea
was because it was Moses who commenced writing the Bible in 1513
b.c.e. and it is only through the Bible that we have any idea of
spiritual matters. The sacrifices commanded under the law covenant all
pointed forward to Jesus Christ and his sacrifice and the benefits
that flowed from that sacrifice [ Hebrews 8;3-5..but which men are
rendering sacred service  in a typical representation, and a shadow [
or copy] of the heavenly things, just as Moses, when about to make the
tent [the Tent of Meeting] in completion, was given the divine
command. For says he; "See that you make all things after their
pattern THAT WAS SHOWN TO YOU IN THE MOUNTAINS"
Hebrews 9;9..This very tent is an illustration for the appointed time
that is now here, and in keeping with it both gifts and sacrifices are
offered. However, these are not able to make the man doing sacred
service perfect as respects his conscience.10. but have to do only
with food and drinks and variouis baptisms . They were legal
requirements pertaining to the flesh, and were imposed until the
appointed time TO SET THINGS STRAIGHT.
Hebrews 10;5-10..Look!, I am come  [ in the role of the book it is
written about me] to do your will, Oh God.
God was humble enough and loved us enough to sacrifice his own son for
us. And all He asks is for us to try and understand and learn to live
peaceably with one another. If I got it a bit wrong, [???] it will be
sorted out, providing I stick with the Bible as I see it written, and
not embellish it with my own ideas. Pug.

Yes, but...the question pertains to "animal sacrifices" (not the
day-to-day services and requirements of the covenent) and the vows
that were made in conjunction with THOSE sacrifices.

We all make mistakes.

tutuzdad-ga