The Need for the Sunnah in order to Understand the Qur’aan, and Examples for that:
Allaah’s statement:
“The male and the female thief – cut off their hands” [Surah Al-Maa’idah: 38] is a good example of this, for the word “thief” mentioned in it, is absolute, as is the case with the word “hand.”
The verbal Sunnah explains the first of these two (words) and restricts it to mean just the thief that steals a quarter of a dinaar. The Prophet صلى الله عليه وسلم: “There is no cutting off of the hand except in (cases where one steals) a quarter of a dinaar and more.”
[Reported by Al-Bukhaaree and Muslim]

Likewise, the Prophet صلى الله عليه وسلم explained the second (word) with his action or with the action of his Companions and his approving of that. This is since they would cut the hand of the thief off from the wrist, as is well known from the books of Hadeeth.

The verbal Sunnah also explains the “hand” that is mentioned in the verse concerning Tayammum:
“Then wipe your faces and hands” [Surah An-Nisaa: 43, Surah Al-Maa’idah: 6] in that it can also refer to the palm.This is based on the Prophet’s saying: “Tayammum is a tap (i.e. wipe) of the face and hands.”
[Reported by Ahmad, Al-Bukhaaree, Muslim and others from the narration of ‘Ammaar bin Yaasir radhi Allaahu anhu]
Below are some other verses from the Qur’aan that cannot be understood correctly, according to what Allaah intended, unless by way of the Sunnah.

1. Allaah says:
“It is those who believe and mix not their Faith with dhulm (wrong) – for them (only) there is security and they are the guided ones.” [Surah Al-An’aam: 82]
The Companions of Allaah’s Messenger صلى الله عليه وسلم understood the phrase “with dhulm (wrong)” according to its general sense, which includes every wrong, even if it be small. This is why they had difficulty understanding the verse and so they said: “O Messenger of Allaah! Which one of us doesn’t mix their Faith with wrong?” So the Prophet صلى الله عليه وسلم said: “It doesn’t mean that. It only means Shirk (here). Didn’t you hear Luqmaan say:
‘Verily Shirk is a great wrong?’ [Surah Luqmaan: 13]”
[Reported by Al-Bukhaaree, Muslim and others]

2. Allaah’s says:
“And when you travel in the land, there is no sin on you if you shorten your prayer, if you fear that the disbelievers may attack you.” [Surah An-Nisaa: 101]
The literal wording of this verse necessitates that shortening the prayer while on a journey can only be done on the condition when one is in the state of fear. This is why some of the Companions asked Allaah’s Messenger: “So then why do we shorten the prayer when we are in a state of security?” He صلى الله عليه وسلم replied: “This is a charity that Allaah has expended to you, so take His charity.”[Reported by Muslim]
3. Allaah says:
“Forbidden to you (for food) are: al-maytatah (dead animals), blood, the flesh of swine…” [Surah Al-Maa’idah: 3]
But the verbal Sunnah explains that deceased locusts and fish, as well as liver and spleen (types) of blood are lawful. The Prophet صلى الله عليه وسلم said: “Two types of deceased animals and two types of blood have been made lawful for us: locusts and sea fish [meaning all types of fish], and the liver and the spleen.”
[Reported by Al- Bayhaqee and others in marfoo’ and mawqoof form. The chain of the mawqoof narration is authentic and it takes on the ruling of being marfoo’ since it cannot be stated based on one’s mere opinion.]
4. Allaah says:
“Say (O Muhammad): ‘I find not in that which has been inspired to me anything forbidden to be eaten by one who wishes to eat it, unless it be maytah (a dead animal) or blood poured forth (by slaughtering), or the flesh of swine (pork), for that surely is impure, or impious (unlawful) meat (of an animal) which is slaughtered as a sacrifice for other than Allaah…’” [Surah Al-An’aam: 145]

Then the Sunnah came and forbade other things that haven’t been mentioned in this ayah, such as the Prophet’s صلى الله عليه وسلم saying: “Every predatory animal that has fangs and every bird that has claws is unlawful (for eating).” There are also other ahaadeeth on this subject that forbid other animals, such as what the Prophet صلى الله عليه وسلم said on the Day of Khaybar: “Verily Allaah and His Messenger forbid you from (eating) domesticated donkeys, for they are impure.” [Reported by Al-Bukhaaree and Muslim]

5. Allaah says:
“Say (O Muhammad): ‘Who has forbidden the adornment with clothes given by Allaah, which He has produced for his slaves, and the good (lawful) things from provision?’” [Surah Al-A’raaf: 32]

But the Sunnah explains that there are certain types of adornments that are forbidden. It is authentically reported that the Prophet صلى الله عليه وسلم went out one day to meet his Companions holding silk in one hand and gold in the other, and said:“These two things are unlawful for the males of my ummah, (but) lawful for the females.” [Reported by Al-Haakim who authenticated it] The ahaadeeth bearing this same understanding are many, well known and can be found in the two Saheeh collections as well as other collections.

There are many more examples like these (above) that are known to the people who have knowledge of Hadeeth and Fiqh. So from what has been stated previously, it should become clear to us, O brothers, the importance of the Sunnah in deriving Islamic laws. For indeed if we look back again at the examples I mentioned before, not to mention those that I didn’t mention, we will have certainty that there is no way to understand the noble Qur’aan, unless we understand it along with the Sunnah.

In the first example, the Companions understood the word “dhulm” mentioned in the ayah according to its literal meaning. This was even though they, may Allaah be pleased with them, were as Ibn Mas’ood said: “The best of this ummah, possessing the most pious of hearts, profound in learning and the least of constraints.” But in spite of this, they erred with regard to understanding that. So if it were not for the Prophet refuting their error and guiding them to what was correct with regard to the meaning of “dhulm” – that it in fact meant Shirk here – we would have followed them upon their error. However, Allaah, Mighty and Majestic, saved us from that due to the grace of the Prophet’s guidance and Sunnah.

And in the second example: if it weren’t for the afore-mentioned hadeeth, we would have remained in doubt, to say the least, regarding shortening the prayer while on a journey in the state of security. That is to say if we wouldn’t have already taken the view of making being in the state of fear a condition, as is literally stated in the ayah. This is also just what the Companions themselves understood (about the ayah) until they saw the Prophet صلى الله عليه وسلم shorten his prayer, and they shortened their prayer along with him, while they were in a state of security.

In the third example: If it weren’t for the hadeeth, we would have been forbidden from foods that were made lawful for us, such as (dead) locusts and fish, and liver and spleen.

In the fourth example, if it weren’t for the hadeeth, which mentions some things (not mentioned in the ayah), we would have made lawful what Allaah had made forbidden through the tongue of the Prophet صلى الله عليه وسلم, such as predatory (fanged) animals and birds with claws.

The same goes for the fifth example, if it weren’t for the ahaadeeth reported in that regard, we would have made lawful that which Allaah made unlawful upon the tongue of the Prophet, such as silk and gold. This is why some of the Salaf used to say: “The Sunnah judges upon the Book (i.e. Qur’aan).”
Org from al-ibaanah eBook:
The Status of Sunnah in Islam – Shaikh Nasiruddin Albanee