regarding sins..

Wa'alaikumsalam

O you who have believed, do not violate the rites of Allah or [the sanctity of] the sacred month or [neglect the marking of] the sacrificial animals and garlanding [them] or [violate the safety of] those coming to the Sacred House seeking bounty from their Lord and [His] approval. But when you come out of ihram, then [you may] hunt. And do not let the hatred of a people for having obstructed you from al-Masjid al-Haram lead you to transgress. And cooperate in righteousness and piety, but do not cooperate in sin and aggression. And fear Allah ; indeed, Allah is severe in penalty.
(Al-Ma'idah: 2)

Salaam.

Even though you might not drink alcohol:
It was narrated from ‘Abdullah ibn ‘Abdullah ibn ‘Umar, from his father, that the Prophet (blessings and peace of Allah be upon him) said: “Allaah has cursed khamr and the one who drinks it, the one who pours it, the one who sells it, the one who buys it, the one who squeezes it, the one for whom it is squeezed, the one who carries it and the one to whom it is carried.”,
Narrated by Ahmad (5716) and Abu Dawood (3674); classed as saheeh by al-Albaani.

Al-Tirmidhi (1295) narrated that Anas ibn Maalik said: The Messenger of Allaah (peace and blessings of Allaah be upon him) cursed ten with regard to wine: the one who squeezes (the grapes etc), the one who asks for it to be squeezed, the one who drinks it, the one who carries it, the one to whom it is carried, the one who pours it, the one who sells it and consumes its price, the one who buys it and the one for whom it is bought.


Warn others of sins they are committing, even if it's very little:
The Prophet (peace and blessings of Allaah be upon him) said: “Whoever among you sees an evil action, let him change it with his hand (by taking action); if he cannot, then with his tongue (by speaking out); and if he cannot, then with his heart (by hating it and feeling it is wrong), and that is the weakest of faith.” Narrated by Muslim (49).

“And it has already been revealed to you in the Book (this Qur’aan) that when you hear the Verses of Allaah being denied and mocked at, then sit not with them, until they engage in a talk other than that; (but if you stayed with them) certainly in that case you would be like them. Surely, Allaah will collect the hypocrites and disbelievers all together in Hell”
[al-Nisa’ 4:140]

Walk away from haram, stay with halal:
Ibn Maajah narrated in his Sunan (2144) that Jaabir ibn ‘Abd-Allaah said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “O people, fear Allaah and be moderate in seeking a living, for no soul will die until it has received all its provision, even if it is slow in coming. So fear Allaah and be moderate in seeking provision; take that which is permissible and leave that which is forbidden.” Classed as saheeh by al-Albaani inSaheeh Ibn Maajah.


It is not permissible to help a kaafir or a Muslim to buy alcohol or to do any other evil or sinful thing. The one who does that is a loser and a sinner. Allaah forbade that in the Qur’aan, when He said (interpretation of the meaning):
“Help you one another in Al-Birr and At-Taqwa (virtue, righteousness and piety); but do not help one another in sin and transgression”
[al-Maa’idah 5:2]


People who help other Muslims commit sins:
This is what Caliph Umar Ibnul-Khattaab had predicted when he said: “Soon the bonds of Islam will be loosened bit by bit, because people will enter into Islam but will be unaware of Jaahiliyyah (ignorant practices that Islam opposes),” meaning that they won’t hesitate to follow them [Ibn Taymiyyah – Majmoo’ul-Fataawaa (10/301)].

“And (remember) the Day when the wrongdoer will bite at his hands, he will say: O! Would that I had taken a path with the Messenger (Muhammad). Ah! Woe to me! Would that I had never taken so–and–so as a friend. He indeed led me astray from the reminder (the Quran) after it had come to me. And Satan is ever a deserter to man in the hour of need” (Al–Furqaan 25: 27–29)

This adds to the good replies above. Allah (swt) says:

You are the best nation produced [as an example] for mankind. You enjoin what is right and forbid what is wrong and believe in Allah . If only the People of the Scripture had believed, it would have been better for them. Among them are believers, but most of them are defiantly disobedient.

[3:110]

Our being the best Ummah for the people hinges upon our enjoining in what good and forbidding evil. What then of one who enjoins sin? It is completely contrary to Islam and what was tied to the word best.