Bismillah.

First of all, what is khums in Islam? And what is khums in shia understanding? In accordance to Islamic texts, khums it is 1/5 of war booty that Muslims are getting after the battles. It should be payed to group of people, as it would be show later from the verse of Quran. 

For rafidah, khums it is 1/5 of income of any Muslim, that shias paying to their marajiah. Famous shia encyclopedia says: The portion of Allah goes to His Messenger to be spent for the path of Allah. After the Prophet passed away, and at the time of the first 11 Imams, the first 3 portions used to go to the Imam of Ahlul-Bayt to be spent in the path of Allah.

Now that we have no access to Imam Mahdi (as), a religious scholar will receive the first three portions (which will be half of total Khums)

Let us have a look what Allah said about this in Quran?

Allah said:

[8:41] And know that out of all the booty (ghanimtum) that ye may acquire (in war), a fifth share is assigned to Allah,- and to the Messenger, and to near relatives, orphans, the needy, and the wayfarer,- if ye do believe in Allah and in the revelation We sent down to Our servant on the Day of Testing,- the Day of the meeting of the two forces. For Allah hath power over all things.

I came across with some shia doubts regarding of usage word (الغنيمة) ghanimat in the Quran. In their attempt to justificate taking the khums from ordinary people, rafidah claims that this word from Quran, mean something other than war booty.

Abu Jafar at-Tusi in his masterpiece commentary of Quran “at-Tibyan li Jamil Ulum al-Quran”, in the explanation of this verse said:

الغنيمة ما اخذ من اموال اهل الحرب من الكفار بقتال. وهي هبة من الله تعالى للمسلمين. والفيء ما اخذ بغير قتال في قول عطا بن السائب، وسفيان الثوري وهو قول الشافعي، وهو المروي في اخبارنا.

“al-Ghanimah it is what is taken from property of people of war (ahlal harb) from disbelievers after the battle. And this is present from Allah to Muslims. al-Feiy is what taken (from them) without battle. In accordance to the words of Ata ibn as-Sayeb , Sufyan as-Sawri, and that is saying of Shafi. AND THIS WAS NARRATED IN OUR REPORTS”

He was echoed by other shia scholar with slight but important difference. Tabarsi in “Majmaul bayan fi tafsir al-Quran” said:

اللغة: الغنيمة ما أخذ من أموال أهل الحرب من الكفار بقتال وهي هبة من الله تعالى للمسلمين والفيء ما أخذ بغير قتال وهو قول عطاء ومذهب الشافعي وسفيان وهو المروي عن أئمتنا

“al-Ghanimah it is what is taken from property of people of war (ahlal harb) from disbelievers after the battle. And this is present from Allah to Muslims. al-Feiy is what taken (from them) without battle. In accordance to the words of Ata imadhhab of Shafi, Sufyan. AND THIS WAS NARRATED from our Imams”

Other shia mufasir, Faydh al-Kashani in his “Tafsir as-Safi” said:

{ (41) وَاعْلَمُواْ أَنَّمَا غَنِمْتُم مِّن شَيْءٍ } قيل أي الذي أخذتموه من الكفّار قهراً.
(And know that out of all the booty (ghanimtum) that ye may acquire), it was said it is mean whatever you took from disbelievers by using the power”.

Other shia mufasir al-Janabezi (d 14 h) said in his commentary “Tafsiru tafsiru bayanu sadah fi maqamatil ibadah”:

اسم الغنيمة قد غلبت على ما كان يؤخذ من الكفّار بالقهر والغلبة حين القتال 

For word ghanimat –  predominant meaning is things which been taken from disbelievers by using power, and during the battle”

So at least these shia scholars confirms following rule:

More correct and predominant meaning for words al-ghanimat – is war booty.

And in this verse Allah Taala used the word GHANIMTUM

وَاعْلَمُوا أَنَّمَا غَنِمْتُمْ مِنْ شَيْءٍ فَأَنَّ لِلَّهِ خُمُسَهُ وَلِلرَّسُولِ وَلِذِي الْقُرْبَىٰ وَالْيَتَامَىٰ وَالْمَسَاكِينِ وَابْنِ السَّبِيلِ إِنْ كُنْتُمْ آمَنْتُمْ بِاللَّهِ وَمَا أَنْزَلْنَا عَلَىٰ عَبْدِنَا يَوْمَ الْفُرْقَانِ يَوْمَ الْتَقَى الْجَمْعَانِ ۗ وَاللَّهُ عَلَىٰ كُلِّ شَيْءٍ قَدِيرٌ {41}

[Yusufali 8:41] And know that out of all the booty that ye may acquire (in war), a fifth share is assigned to Allah,- and to the Messenger, and to near relatives, orphans, the needy, and the wayfarer,- if ye do believe in Allah and in the revelation We sent down to Our servant on the Day of Testing,- the Day of the meeting of the two forces. For Allah hath power over all things.

Let us now have a look to the words of shia Imams.

Ibn Babaweyh al-Qummi, shaykh Saduq in his book “Man la yahdurhul faqih” 2/40, narrated:

١٦٤٦ ـ وروى الحسن بن محبوب ، عن عبد الله بن سنان قال : سمعت أبا عبد الله عليه‌السلام يقول : « ليس الخمس إلا في الغنائم خاصة »

Translation:

From al-Hasan ibn Mahbub, from Abdullah ibn Sinan: I heard Abu Abdullah (Jafar as-Sadiq) said: There is no khums except from GHANIMAT (war booty)

Hurr al-Amili in Wasail 9/480, after narrating this hadith, said:

It means from outward of Quran khums isn’t obligation except if not from ghanimat, as for other than this, it is established by Sunnah.

Basically, he is clear that from Quranic usage of word ghanimat he understands nothing but war booty, and khums from other than ghanimah (see shia laymen regular income) established from Sunnah.

Above mentioned report was not suitable for modern shias, we can see that from the note of muhaqiq of the “Man la yahdurhul faqih”, he said in the footnote to this report:

إن كان المراد غنائم دار الحرب فظاهر هذا الخبر التقية

Translation:

“If here (Imam) mean ghanimatu of darul harb (it means war booty of battlefield) this report is taqiyyah as obvious”

In order to protect their rights to collect khums from ordinary shias, this man without any shame accused Imam Jafar as-Sadiq in telling lies to people in regards of Shariah Rulings!

Authenticy of hadith:

1) It is not a secret for my knowledgeable shia brothers, that shaykh Saduq himself accepted his entire book as a sound one.  He said:

He writes:

وصنفت له هذا الكتاب بحذف الأسانيد لئلا تكثر طرقه وإن كثرت فوائده ولم أقصد فيه قصد المصنفين في إيراد جميع ما رووه بل قصدت إلى إيراد ما أفتي به وأحكم بصحته وأعتقد فيه أنه حجة فيما بيني وبين ربي تقدس ذكره وتعالت قدرته

“I have compiled this book for him without chains of transmission, so that its transmissions should not be too many while its benefits are abundant. I did not intend to present all of what they have narrated, as authors usually do; rather I intended to present that by which I give legal opinions and rule to be authentic [aĥkum bi şiĥĥatih], and believe that it is proof [ĥujja] between me and my Lord, exalted is His power.”

 Source:Man lā Yaĥđuruh al-Faqīh, of Ibn Bābawayh al-Qummī (d. 381), volume 1, page 2-3 [Qum]; Man lā Yaĥđuruh al-Faqīh, of Ibn Bābawayh al-Qummī (d. 381), volume 1, page 3 [Lucknow]

Contemporary Shī`ī scholar and intellectual, Dr. `Abd al-Hādī al-Fađlī, writes after quoting these words of Ibn Bābawayh:

ونصه هذا واضح وصريح في أنه يعتقد بصحة ما في كتابه ويراه حجة بينه وبين الله تعالى

“This explicit statement of his is clear and unequivocal in showing that he believes in the authenticity of what is in his book, and views it to be proof between himself and Allāh the Exalted.”

Source: Uşūl al-Ĥadīth, of `Abd al-Hādī al-Fađlī, page 217 [Beirut]

This is further confirmed by al-Tabrīzī, who states about Ibn Bābawayh and his book:

وقد صرح لصحة أحاديثه بقوله في مقدمته قصدت إلى إيراد ما أفتي به وأحكم بصحته وأعتقد فيه أنه حجة فيما بيني وبين ربي

“He has declared the authenticity of its narrations in his introduction,with his statement: ‘I intended to present that by which I give legal opinions and rule to be authentic [aĥkum bi şiĥĥatih], and believe that it is a proof [ĥujja] between me and my Lord.’”

Source:Mu`jam al-Maĥāsin wa al-Masāmī, of Abū Ţālib al-Tabrīzī, page 17 [Qum]

Another thing worthy of mention here is what is mentioned in the transcribed lectures of the contemporary Grand Āyat Allāh `Alī al-Sīstānī about Ibn Bābawayh and his book:

إنه قدس سره قد شهد في مقدمة كتابه بصحة جميع ما رواه فيه حيث قال ولم أقصد فيه قصد المصنفين في إيراد جميع ما رووه بل قصدت إلى إيراد ما أفتي به وأحكم بصحته وأعتقد فيه إنه حجة فيما بيني وبين ربي تقدس ذكره وتعالت قدرته

“Verily, he—may Allāh sanctify his secret—has certified the authenticity of all that he has narrated in it, in the introduction, when he said: ‘I did not intend to present all of what they have narrated, as authors usually do; rather I intended to present that by which I give legal opinions and rule to be authentic [aĥkum bi şiĥĥatih], and believe that it is proof [ĥujja] between me and my Lord, sacred is His mention and exalted is His power.’”

Source: Qā`ida lā Đarar wa lā Đirār, of `Alī al-Sīstānī, page 87 [Qum]

2) Chain of hadith contains two narrators. a) al-Hasan ibn Mahbub, thiqah jalil, like he was described in RIjal of ibn Dawud al-Hilli p 77. b) Abdullah ibn Sinan.  Abdullah ibn Sinan ibn Tarif Kufi  thiqah. See Rijal of Najashi p 214.