We must not co-operate in sinful deeds

It is also Haraam to help an oppressor whose oppression is not directed to others; but he is unjust to himself. For example to omit prayers and avoid fasting, to drink wine, commit adultery, gambling etc. Every type of sinner is being unjust to himself. Hence helping him in being unjust to himself is also prohibited. One who helps him is his partner in sin. The Almighty Allah has mentioned: 
"Help one another in goodness and piety, and do not help one another in sin and oppression, and be careful of (your duty to) Allah, surely Allah is severe in requiting (evil)."
(Surah Maidah 5:2)

Sin (ithm) is limited to the one who commits it and aggression (udwaan) affects others too.

All the proofs and arguments that are applicable to the obligation of forbidding evil also apply here.

Helping in Sin

To help in any condition required in a sinful act is Haraam.

(1) For example to sell grapes with the specific purpose of making wine.

(2) A person may help in some way without the intention of helping towards a sinful act, for example, he may sell grapes to a wine-maker without the intention of this being used for making wine, but if there is no other source available for the wine maker to procure grapes, then the selling of grapes by this person is haraam, because it would directly contribute to the manufacture of wine.

Helping a sinner in some other way

Is it allowed to help a sinful person, by way of giving loan or solving his difficulties to one who does not pray or is an alcoholic? Sometimes it is very difficult to decide as to what is the proper course of action in such circumstances, because we are commanded to maintain a distance from sinners. Thus Ali (a.s.) says: 
"The Messenger of Allah has ordered us to be unfriendly with the sinful people." 
(Wasaelush Shia)

Hazrat Imam Sadiq (a.s.) rebuked his followers: 
"It may happen that in your social circle one of your Shias does evil, and you do not prevent him nor dissociate with him nor hurt him, till he gives up his evil deeds." 
(Tehzeeb)

There are several traditions regarding certain specific sins. For example: 
"One who helps a person who does not pray, with a morsel of food or a piece of cloth, is as if he has murdered seventy Prophets, the first of whom being Adam (a.s.) and the last, Muhammad (s.a.w.s.)." 
(Layali Akhbaar)

In another tradition the Holy Prophet (s.a.w.s.) says: 
"One who smiles at a person who does not pray, is as if he had demolished the Holy Ka'ba seventy times." 
(Layali Akhbaar)

The Prophet of Allah (s.a.w.s.) also says: 
"One who helps a person who does not pray, with a drink of water, is as if he has made war upon me." 
(Layali Akhbaar)

Other traditions of this kind are against associating with alcoholics, with those who cut off relationships with their kith and kin and with liars. On the other hand we have traditions that emphasise the respecting of a believer's rights, helping and socialising with the followers of Ahlul Bayt (a.s.), the Sayyads, the neighbours etc.

The latter kinds of traditions are not conditional. For example it is obligatory to do Sileh Rahem with one's kindered and it is not a necessary condition that the relatives should be pious. We have discussed this matter in the chapter of Sileh Rahem and the rights of parents. Even if they are unbelievers we have to fulfill our duties towards them. In the same way the Holy Prophet (s.a.w.s.) says regarding Sayyads: 
"Respect my descendants, be kind towards the righteous from among them for the sake of Allah and towards the non-righteous ones for my sake."

Imam Reza (a.s.) says the following with regard to the devotees of the Progeny of Muhammad (s.a.w.s.): 
"Be a friend of the Progeny of Muhammad even if you are a trangressor and befriend their friends even if they are transgressors."

As far as the rights of neighbours are concerned we are told that if your neighbour is a Muslim he has double rights upon you (One of neighbourhood and another of being a fellow Muslim). If he is an infidel he still has the right of neighbourhood on you. 
(Mustadrakul Wasael)

On the basis of the above it is incumbent to befriend the followers of Ahlul Bayt (a.s.), help them and fulfill their needs even if they are not pious. We must respect the Sayyads and fulfill our rights towards the kindered even if they are sinners.

Secondly when one is faced with more than one obligation at a time, one should try to fulfill all if it is easy to do, if this is difficult, one should fulfill the one which is more important.

For example when one is faced with a situation when one is keeping an obligatory fast and a child is drowning in a pond. If he jumps into the pool his head will submerge and the fast will become invalid, but since it is more important to save a human life it becomes Wajib for him to jump into the pool. According to Shariat breaking a fast is a lesser evil than allowing the death of a human. By doing this he would not be liable for the punishment of breaking a Wajib fast. On the other hand he will be deserving of Divine reward for saving a human life.

Preventing others from evil is most important

Enjoining good and forbidding evil are the Divine commands, which are obligatory to be followed. They are so important that in case of their clashing with other duties, priority has to be given to these comands. If mother, father, son or some relative do not obey the divine obligatory commands like praying etc. And if by withholding kindness and help from them, it is possible to reform them and induce them to give up their sinful ways, then it is wajib to withhold kindness and help from them. The same reasoning applies to Sayyeds, neighbours and the followers of Ahlul Bayt (a.s.) who have a right on us. But if withholding help is not going to make any difference in their behaviour, then it is meaningless to adopt such measures. For these were witheld only that they may force the sinners to reform. Otherwise there is no point in employing these retaliatory tactics. If one's parents and relatives are not in the habit of ritual prayers and dissociating with them will not change their attitude; then it is Haraam to dissociate with them or disobey them.

We must discriminate between different ranks and positions

We must remember that Nahy Anil Munkar (Forbidding evil) is more important than the rights of relatives, Sayyads and neighbours. Hence we should first try to fulfill the duty of forbidding evil even if it necessitates the non-fulfillment of latter duties, provided there is scope of improvement among the sinners. If it is not so, then it is not required to dissociate with them or withhold kindness etc. from them.

And as far as possible we should try an adopt a charitable option. If it is possible to reform a sinner through love and help we must try it, before we resort to harsher ways of withholding kindness and help. For example, a father has better chances of influencing a son, who is not steadfast in his prayers, if he tries to influence him gently. A gentle option must be tried before taking strict measures against him.

In other words, when withholding kindness does not achieve the desired results (giving up of sinful ways) there is no prohibition in being kind. In fact it is an obligatory act and its omission is Haraam.