What is the ruling on someone (muslim)
saying lies about his other brother.i.e saying he drinks Alcohol and other sort of things.

Praise be to Allaah.

Accusing a Muslim of doing an evil deed without proof is a
major sin which deserves punishment. Talking about it to other people is a kind of gheebah
(backbiting, gossip) which Allaah has forbidden and likened to a person eating the flesh
of his dead brother, as He says (interpretation of the meaning):

“… neither backbite one another. Would one of you like to eat
the flesh of his dead brother? You would hate it (so hate backbiting). And fear Allaah.
Verily, Allaah is the One Who accepts repentance, Most Merciful.”[al-Hujuraat 49:12]

“Verily, those who like that (the crime of) illegal sexual should be
propagated among those who believe, they will have a painful torment in this world and in
the Hereafter…” [al-Noor 24:19].

Whoever slanders his brother or accuses him of an evil deed has to repent
to Allaah, ask his brother’s forgiveness, and avoid everything that causes harm to a
fellow Muslim. Abu Hurayrah (may Allaah be pleased with him) reported that the Prophet

(peace and blessings of Allaah be upon him) said: “Whoever believes in Allaah and the
Last Day, let him say something good or else remain silent.” (Reported by
al-Bukhaari, 11/256, and by Muslim, no. 47). Abu Dharr (may Allaah be
pleased with him) said: “I heard the Messenger of Allaah
(peace and blessings of
Allaah be upon him) say: ‘No man accuses another of an immoral deed or kufr, but it
will come back on him, if the person he accuses is not as he says he is.’” (Reported
by al-Bukhari, 10/388). Accusing a Muslim of drinking wine is the same as
accusing him of an immoral deed (fisq), and whoever accuses his brother of
something he is not guilty of, Allaah will make him fall into the thing he of which he
accused his brother. A man was brought to ‘Abd-Allaah ibn ‘Abbaas, and he was
told, “This is so and so, his beard was dripping with wine.” [Ibn ‘Abbaas]
said, “We were forbidden to spy on others, but if something is obvious to us, we will
accept it and act accordingly.” (Reported by Abu Dawood, 4890, who said it is
a saheeh hasan hadeeth).

It is not permissible for the Muslim to spy on his Muslim
brother or to seek out his faults. If he accidentally sees him in a doubtful place or
seeming to behave in a doubtful manner, he should not accuse him unless he sees him with
his own eyes doing a wrongful action. He should advise and counsel him, then if he insists
on doing that thing, and there is fear that he may harm other Muslims, or if one is asked
about him for a legitimate reason, then he should tell those who have something to do with
it about what he knows. But he should not broadcast it unless the person does the evil
action openly, because this will only help the Shaytaan against him and stop him from
repenting. And Allaah knows best.