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.
If someone who has recently converted to Islam drinks alcohol, he is not to be blamed for that if he does not know that this act is prohibited in Islam. It is conditioned, for executing the prescribed punishment for drinking alcohol, that the perpetrator knows about its being prohibited. It was reported that ‘Umar and Ali said that the prescribed punishment is to be executed only when the perpetrator knows of the prohibition of the act that he has committed. If the person in question knows that drinking alcohol is prohibited, then he should be punished according to the way prescribed by the Sharee'ah; which is lashing, for whoever drinks alcohol, regardless of whether it is much or little. This is based on the Hadeeth in which the Prophet, sallallaahu ‘alayhi wa sallam, said: “Whoever drinks alcohol, whip him.” [Abu Daawood and others]
The majority of scholars view that the legal punishment for drinking alcohol is eighty lashes, for that is what ‘Umar applied. Furthermore, all the companions agreed with ‘Umar's practice during the time of his caliphate. Some companions, however, renounced this opinion after the death of ‘Umar and said that the prescribed punishment for drinking alcohol is forty lashes only.
Allaah Knows best.