I live in a country where blasphemy and cursing the Companions, may Allaah be pleased with them, is common. What is the ruling on praying behind Imaams who do this and on eating the meat they slaughter?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

It is a grace from Allaah The Almighty that He has given us signs and criteria to identify Muslims and non-Muslims. Anyone who adheres to the rules and laws of Islam is a Muslim, entitled to a Muslim's rights and directed to fulfill whatever obligations they must meet. A person, sect or group who meets this criteria is considered Muslim.  On the other hand, breaking the limits of Islam makes someone a non-Muslim.  Thus, this person is treated according to the rulings related to non-Muslims.

Blasphemy is an act that nullifies the faith of its committer. Is'haaq Ibn Raahawayh quoted a consensus of scholars when saying that those who blaspheme Allaah The Exalted or the Prophet, sallallaahu ‘alayhi wa sallam have thereby committed apostasy.

A Muslim turns into an apostate if he mocks any aspect of Islam, or its promised reward or punishment. The verse that reads (what means): {And if you ask them, they will surely say, "We were only conversing and playing." Say, "Is it Allaah and His verses and His Messenger that you were mocking?" Make no excuse; you have disbelieved after your belief.} [Quran 9:65-66] supports this.

Associating partners with Allaah also turns a Muslim into an apostate, as does cursing the Companions . So anyone who insults them in a way that accuses the credibility of their uprightness and faith is a disbeliever.  Imaam Ahmad said that anyone who insults Abu Bakr, ‘Umar or ‘Aa’ishah is not considered a Muslim.

However, someone may ask why does a Muslim become an apostate if he or she criticizes the Companions? The answer is that the Companions were the bearers of the Quran and the callers to Islam, whom Allaah The Almighty chose to be companions of His Prophet, sallallaahu ‘alayhi wa sallam, and whom he purified, refined, was pleased with and praised in the Quran, as in the verse that Says (what means): {And the first forerunners [in the faith] among the Muhajireen and the Ansar and those who followed them with good conduct - Allaah is pleased with them and they are pleased with Him, and He has prepared for them gardens beneath which rivers flow, wherein they will abide forever. That is the great attainment.} [Quran 9:100] affirms.

Moreover, the Prophet, sallallaahu ‘alayhi wa sallam, warned against affronting them. It is narrated that he forbade slurring the Companions and said that nobody's spending, no matter how great it was, would be equal to a small sacrifice of the Companions in the cause of the religion. [Al-Bukhari, Muslim, Ibn Abi Shaybah]

In another authentic Hadeeth the Prophet sallallaahu ‘alayhi wa sallam was reported to have prohibited his Companions to be insulted and he cursed whoever does so. [At-Tabraani: Al-Awsat]

Based on this, it is a serious crime to insult the Companions, claim they are apostates or to allow the permissibility of slurring them, even without doing so. This crime turns a person into an apostate. The same ruling applies to anyone swearing at Abu Bakr and ‘Umar or those who speak unfavorably of ‘Aa‘ishah accusing her of what she has already been declared innocent of in the Quran.

And likewise is the one who believes that the copy of the Quran adopted by Muslims now is incomplete or that Jibreel (Gabriel) incorrectly conveyed the message.

Thus it is impermissible to be led in prayer, marry, give in marriage or consume lawfully edible animals slaughtered by anyone who has done such beliefs or actions, and such people must not be dealt with as other Muslims are. However as a person who is afflicted by living in their areas or if you happen to work with them, you must use your judgment and wisdom and not be deceived by them and should guard against their plots and cunning. It is also permissible to greet them or return their greetings if there is a potential benefit, or to ward off harm.

However, the ruling is different in the case of a person who is traced back to those who insult the Companions but does not himself hold such corrupt beliefs. This person may be treated as a Muslim, prayed behind, and it is permissible to eat his slaughtered animals. However, since these people are few in number, you must be sure of their beliefs before proceeding.

Allaah Knows best.