Is he sinning if he ignores the view of someone who gave him a fatwa because he did not mention the evidence for his fatwa?

Praise
be to Allah

Firstly:

It is obligatory
for the one who gives a fatwa concerning some religious matter to have
knowledge about the matter concerning which he gives a fatwa, whether he
rules it to be permissible or prohibited. Whoever knows something may speak
of it, and whoever does not know should refer the matter of what he does not
know to one who does know it.

Allah, may He be
exalted, says (interpretation of the meaning):

“And
do not say about what your tongues assert of untruth, ‘This is lawful and
this is unlawful,’ to invent falsehood about Allah . Indeed, those who
invent falsehood about Allah will not succeed”

[an-Nahl 16:116].

As-Sa‘di (may
Allah have mercy on him) said:

That is, do not
declare things to be prohibited or lawful of your own accord, fabricating
lies against Allah and attributing to Him words that He never said.

End quote from
Tafseer as-Sa‘di (p. 451)

Abu Dawood
(3657) narrated that Abu Hurayrah said: The Messenger of Allah (blessings
and peace of Allah be upon him) said: “Whoever is given a fatwa that is not
based on knowledge, his sin is borne by the one who gave the fatwa.”

Classed as hasan
by al-Albaani in Saheeh Abi Dawood.

Shaykh Ibn Baaz
(may Allah have mercy on him) said:

One of the
gravest of crimes is issuing fatwas without knowledge; how many have gone
astray and been doomed as a result of that, especially if the fatwa was
utter in front of many people and came from one by whom some people were
deceived. The dangers posed by that are great, and the consequences are
severe. The one who issues fatwas without knowledge will bear a burden of
sin like that of those who follow him.

End quote from
Majmoo‘ Fataawa Ibn Baaz (3/219).

Secondly:

With regard to
accepting the view of one who says that something is unlawful or something
is obligatory, but does not offer any evidence for that:

If the one who
says that is not one of the well-known scholars, then he should not be
followed in this opinion, and it is not obligatory for the one who hears him
to accept his opinion or to follow it.

But if he is a
scholar who is known for his knowledge and trustworthiness, then it depends:

If the one who
asked him is a seeker of knowledge who can understand the evidence when it
is presented to him and is able to check its validity, then he is not
obliged to follow him just because he said that, until he explains to him
the basis of his opinion and his evidence, because the seeker of knowledge
is able to research the matter, find out about different views on a
particular issue, weigh up the evidence and determine which evidence is
stronger.

But if the one
who asked him is an ordinary Muslim who is not able to understand the basis
of the scholar’s view, and cannot weigh up the evidence and determine which
is stronger, then he is obliged to follow the opinion of the mufti. This is
what is required in his case, as Allah, may He be exalted, says
(interpretation of the meaning):

“So
ask the people of the message if you do not know”

[an-Nahl 16:43].

Moreover, not
referring to a scholar and accepting his opinion causes people to miss out
on knowledge altogether and leads to neglect of shar‘i rulings, and it opens
the door to toying with the religion and following views that are contrary
to the teachings of Islam.

But if he has
any doubts about a scholar’s opinion, he may ask him about the evidence for
that, if he is able to understand it when it is explained to him.

But what is
better in his case, if he has any doubts, is to ask another scholar, one of
those who are known for their religious commitment and trustworthiness, for
the sake of his peace of mind and in order to ward off doubt and anxiety,
not by way of toying with the religion, seeking out concessions or looking
for errors on the part of the scholars.

If the
questioner asks the mufti for evidence, then the mufti must explain it to
him.

Ibn al-Qayyim
(may Allah have mercy on him) said:

The mufti must
explain the evidence and basis for his ruling as much as possible, and he
should not present his fatwa to the questioner on its own, without the
evidence and basis for his ruling. If he does that, this shows that he is
not a qualified scholar and that his share of knowledge is very little. The
one who reflects upon the fatwas of the Prophet (blessings and peace of
Allah be upon him), whose word constitutes evidence in and of itself, will
see that they highlighted the wisdom behind the ruling and the proof of its
soundness.

End quote from
I‘laam al-Muwaqqi‘een, 4/123

Some muftis may
not mention the evidence for their ruling because it is very subtle and the
ordinary Muslim may not be able to comprehend it. The evidence may be based
on an analogy (qiyaas) or some principle of fiqh or usool, and so on.

An-Nawawi (may
Allah have mercy on him) said:

The ordinary
Muslim should not ask the mufti for evidence or say: Why did you say such
and such? If he wants to put his mind at rest by hearing the evidence, he
may ask for it on another occasion, or in the same meeting after accepting
the fatwa as it is.

End quote from
Aadaab al-Fatwa wa’l-Mufti wa’l-Mustafti (p. 85).

An-Nawawi also
said:

It is not wrong
for the mufti to mention the evidence in his fatwa, if it is a clear and
brief text.

As-Saymari said:
He need not mention the evidence if he is giving a fatwa to an ordinary
Muslim, but he may mention it if he is giving a fatwa to one who has
knowledge, such as one who asks him about doing the marriage contract
without a guardian. In that case it is good for him to say: The Messenger of
Allah (blessings and peace of Allah be upon him) said: “There is no marriage
without a guardian”; or if he asks about taking back a divorced wife with
whom the marriage was consummated, he may say: He may take her back, because
Allah, may He be exalted, says (interpretation of the meaning):
“And
their husbands have more right to take them back”
[al-Baqarah 2:228].

End quote from
al-Majmoo‘ (1/52).

What may be
understood from this is that if he is giving a fatwa to an ordinary Muslim,
and the evidence is not a brief, clear text, then there is nothing wrong
with him not mentioning the evidence in his fatwa.

For more
information, please see the answer to question no.
148057

And Allah knows
best.