I have a question abou this verse:

Al kahf – ayah 5

They (Christians) have no knowledge of it, nor had their fathers. Grave is the word that comes out of their mouths; they speak not except a lie.

What do they mean with nor had their fathers. For example if the son of a sheikh who knows every single word of the quran converted to Christianity. Does that mean his father has no knowledge?

Praise
be to Allah

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


“[All] praise is [due] to Allah, who has sent down upon His Servant the Book and has not made therein any deviance.


[He has made it] straight, to warn of severe punishment from Him and to give good tidings to the believers who do righteous deeds that they will have a good reward


In which they will remain forever


And to warn those who say, ” Allah has taken a son.”


They have no knowledge of it, nor had their fathers. Grave is the word that comes out of their mouths; they speak not except a lie.


[al-Kahf 18:1-5]
.

The words “And to warn those (Jews, Christians, and
pagans) who say, ‘Allah has begotten a son (or offspring or children)

refer to the Jews, Christians and polytheists who uttered these abhorrent
words. They were not speaking on the basis of knowledge or certainty,
whether that was their own knowledge or knowledge from their forefathers
whom they were imitating and following. Rather they were following nothing
but conjecture and their own whims and desires.

Mighty is the word that comes out of their mouths
that is, it is mightily abhorrent and the punishment for it will be severe.
What can be more abhorrent than describing Him as having begotten offspring,
which would imply imperfection on His part, association of another with Him
in the unique attributes of Lordship and divinity, and telling lies against
Him?

Hence Allah says: “They utter nothing but a lie” that
is, it is pure lies in which there is no truth at all.

Think about how the Quran nullifies this view gradually,
moving from one thing to another that is even more false. First of all Allah
says, “No knowledge have they of such a thing, nor had their fathers”.
Undoubtedly speaking about Allah without knowledge is prohibited and false.
Secondly, He states that this is a mightily abhorrent thing to say, as He
says: “Mighty is the word that comes out of their mouths.

Then, thirdly, He describes the degree of offensiveness,
which is a lie that is contrary to truth.

See: Tafseer as-Sa‘di (p. 469).

What is meant by the words “No knowledge have they of such
a thing, nor had their fathers
” is that they spoke words of falsehood
concerning which they had no knowledge, and neither did their fathers who
preceded them in uttering these false words. Then their children came and
followed their fathers in that. This is something that neither they nor
their fathers from whom they learned it knew or understood.

What is meant by fathers here is their forefathers who spoke
these false and corrupt words. They were speaking on the basis of
speculation and their own whims and desires, and their children followed
them in that. So it is false words that were uttered by the sons without
knowledge, following their ignorant, lying forefathers in that. How terrible
it is for a man to be ignorant and to follow others in ignorance.

Ash-Shawkani (may Allah have mercy on him) said:

They had no knowledge of that at all, and neither did their
fathers have knowledge. Rather, according to their own claim, they were
following misguidance and their children followed them, so all of them went
astray. End quote.


Fath al-Qadeer

(3/320)

The scholars have stated that what is meant by fathers here
is the fathers who spoke these corrupt words, and their children learned
them from them.

Ibn ‘Atiyyah (may Allah have mercy on him) said:

The words “nor had their fathers” mean: those from
whom these people took this view. End quote.


Tafseer Ibn ‘Atiyyah

(3/495).

Ash-Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said:

nor had their fathers” who said such words. They had
no knowledge concerning that; it was nothing but illusions that they thought
were real, and that is not knowledge. End quote.


Tafseer al-‘Uthaymeen/al-Kahf

(p. 13)

Ibn ‘Ashoor (may Allah have mercy on him) said:

They used to say “We found our fathers following a certain
way and religion, and we will indeed follow their footsteps” [az-Zukhruf
43:23]
. If their fathers did not have any proof for what they said, then
they did not deserve to be followed. End quote.


At-Tahreer wa at-Tanweer

(15/251)

As for fathers who do not believe in such corrupt views,
rather they believe in Allah and affirm His Oneness (Tawheed), they are not
referred to in this verse.

If someone is a believer in the Oneness of Allah, and he has
a son who apostatises from Islam and becomes a Christian, and begins to say
that the Messiah is the son of God, that monotheist father is not to be
criticised or blamed, and he is not to be described as lacking in knowledge
because of what his son did. Rather every individual is to be criticised or
praised on the basis of what he himself does, not what anyone else does.

Abu Dawood (4495) narrated that Abu Rimthah said: I went to
the Prophet (blessings and peace of Allah be upon him) with my father, then
the Prophet (blessings and peace of Allah be upon him) said to my father:
“Is this your son?” He said: Yes, by the Lord of the Ka‘bah. He said: “Is it
true?” He said: I bear witness to it. The Messenger of Allah (blessings and
peace of Allah be upon him) smiled at my resemblance to my father and my
father’s oath concerning me, then he said: “You are not accountable for his
wrongdoing and he is not accountable for yours.” And the Messenger of Allah
(blessings and peace of Allah be upon him) recited the verse: “no bearer of
burdens shall bear the burden of another” [al-An‘am 6:164]

Classed as saheeh by al-Albani in Saheeh Abi Dawood.

Al-Qari (may Allah have mercy on him) said in Mirqat al-Mafateeh
(6/2272):

“You are not accountable for his wrongdoing” i.e., you are
not responsible for his sin; “and he is not accountable for yours” i.e., he
is not responsible for your sin. End quote.

Al-‘Ayni (may Allah have mercy on him) said:

Thus the Messenger of Allah (blessings and peace of Allah be
upon him) confirmed what Allah stated, that each person is responsible for
his own wrongdoing, just as his good deeds are to his own credit, not the
credit of anyone else. End quote.


‘Umdat al-Qari

(8/79).

And Allah knows best.