In Amos 2:12, God criticizes the Israelites for giving wine to the Nazirites. This was a no-no because the Nazirites were not supposed to drink alcohol during the fulfillment of their vow.
The specifics of the Nazirite vow are contained in Numbers 6. In a sense, a person who takes a Nazirite vow places himself in a priestly condition for a period of time. Like the high priest, he is not to defile himself through contact with a corpse, even if it belongs to someone from his immediate family (cp. Numbers 6:7 and Leviticus 21:11). Another possible similarity between Nazirites and priests is that the Nazirites cannot shave their heads for the duration of their vow, and the priests cannot "make bald spots upon their heads, or shave off the edges of their beards" (cp. Numbers 6:5 and Leviticus 21:5). And the Nazirite is not to drink wine, as priests are forbidden to drink alcohol when they enter the tent of meeting (cp. Numbers 6:3 and Leviticus 10:9). Becoming a Nazirite is entering a state of greater holiness, which requires more purity than the average Israelite must assume.
What was the purpose of the vow? In the Hebrew Bible, vows often occur within a quid pro quo context. The worshipper essentially tells God, "Look, if you do this for me, then I will do this for you." We see this scenario with the vows of Jacob (Genesis 28:20), the Israelites at war with Canaan (Numbers 21:2), Jephthah (Judges 11:30), Hannah (I Samuel 1:11), and Absalom (II Samuel 15:7-8).
Vows are serious in the Hebrew Bible. Jephthah performed his vow, even though it meant that he had to sacrifice his daughter. Deuteronomy 23:21-23 says that people who do not keep their vows are guilty before God. And Ecclesiastes 5:4-6 says that it is better not to vow than to make a vow and then break it. In case that point is not clear enough, v 6 threatens that God can destroy the work of a person's hands.
And the Nazirite vow was no joke, for a person in the process of fulfilling it could not even bury his own parents. If he accidentally encountered a dead body, however, then he had to shave his head, offer some sacrifices, and start from scratch (Numbers 6:9-12). But he could do that only if someone suddenly died near him, a situation that he could not control. Overall, he had to keep his vow, for that indicated his respect for God.
When the Israelites of Amos 2:12 give the Nazirites wine to drink, they are showing disrespect to God, for they do not honor the vow that the Nazirites have made to him. But they also are not respecting the Nazirite's personal relationship with God, for they are trying to get him to disregard it. God wants people to honor their commitments to him, and it doesn't help matters when someone is seeking to undermine them through stumbling-blocks.
This concept helps me to better understand passages such as Romans 14 and I Corinthians 8 in the New Testament. In both passages, God is concerned about the personal qualms that characterize the walks of certain Christians. Some Christians did not want to eat meat, particularly when it was offered to idols. Some preferred not to drink alcohol. Some respected specific days. Essentially, they chose to honor God through abstention or the celebration of days. And Paul did not look down on those who did such things, for he says in Romans 14:6, "Those who observe the day, observe it in honor of the Lord. Also those who eat, eat in honor of the Lord, since they give thanks to God; while those who abstain, abstain in honor of the Lord and give thanks to God."
Paul also says that the "stronger" Christians who eat and drink what they like are not to put a stumbling-block in the paths of their "weaker" brothers and sisters. He even goes so far as to say in Romans 14:21, "[I]t is good not to eat meat or drink wine or do anything that makes your brother or sister stumble." Basically, we are to avoid offensive behaviors that can influence others to transgress their consciences. And I have a problem with that concept. In my mind, it seems to give easily-offended Christians the God-given authority to control my own life. Should I avoid going to the movies because an anti-movies Christian might see me entering the theater and become offended? If a Christian drinks a beer at a restaurant, should he have to get rid of his drink if he sees a teetotaler Christian? Maybe the anti-movies and the tee-totaler Christians should learn some tolerance themselves. They should recognize that not everyone in the world has the same qualms that they have, rather than seeking to impose their preferences on everyone else.
Of course, I wouldn't deliberately get in anyone's face. I just have problems with professional weaker brothers (as Chuck Swindoll calls them) trying to run my life. At the same time, I believe that I should respect the personal covenants that people make with God, rather than seeking to undermine them.