Ibn al Hajar says:
The most correct definition which I have found regarding the Sahabah is: That person who met the Rasul of Allah salla Llahu ‘alayhi wa sallam in the condition of believing in him and had passed away as a Muslim.
So, based on the aforementioned, the Ahlul Bayt who accepted Islam in the time of the Rasul of Allah salla Llahu ‘alayhi wa sallam will also be regarded as Sahabah. This is the reason why many books will mention the Sahabah without distinguishing the Ahlul Bayt from them.
The proofs of the virtues of the Sahabah are many:
ْكُنْتُم خَيْرَ أُمَّةٍ أُخْرِجَتْ لِلنَّاسِ
You are the best nation produced [as an example] for mankind.
If the Sahabah are not the first ones to be included in the verse then who else will be included?
وَكَذٰلِكَ جَعَلْنٰكُمْ أُمَّةً وَسَطًا
And thus We have made you a median [i.e., just] community
Wasata here refers to the best of people. The Sahabah (in whom the Ahlul Bayt are included) are the first people who would qualify to be from amongst this group.
لَقَدْ رَضِىَ اللَّهُ عَنِ الْمُؤْمِنِيْنَ إِذْ يُبَايِعُوْنَكَ تَحْتَ الشَّجَرَةِ فَعَلِمَ مَا فِيْ قُلُوْبِهِمْ فَأَنْزَلَ السَّكِيْنَةَ عَلَيْهِمْ وَأَثَابَهُمْ فَتْحًا قَرِيْبًا
Certainly was Allah pleased with the believers when they pledged allegiance to you, [O Muhammad], under the tree, and He knew what was in their hearts, so He sent down tranquillity upon them and rewarded them with an imminent conquest.
The pleasure of Allah is eternal. When Allah declares his pleasure for a particular group then it denotes that Allah is perpetually pleased with them, and they will never incur His wrath.
وَالسَّابِقُوْنَ الْأَوَّلُوْنَ مِنَ الْمُهَاجِرِيْنَ وَالْأَنصَارِ وَالَّذِيْنَ اتَّبَعُوْهُمْ بِإِحْسَانٍ رَّضِيَ اللَّهُ عَنْهُمْ وَرَضُوْا عَنْهُ وَأَعَدَّ لَهُمْ جَنَّاتٍ تَجْرِيْ تَحْتَهَا الْأَنْهَارُ خَالِدِيْنَ فِيْهَا أَبَدًا ذٰلِكَ الْفَوْزُ الْعَظِيْمُ
And the first forerunners [in the faith] among the Muhajirin and the Ansar and those who followed them with good conduct – Allah is pleased with them and they are pleased with Him, and He has prepared for them gardens beneath which rivers flow, wherein they will abide forever. That is the great attainment.
يٰاَيُّهَا النَّبِيُّ حَسْبُكَ اللهُ وَمَنِ اتَّبَعَكَ مِنَ الْمُؤْمِنِيْنَ
O Prophet, sufficient for you is Allah and for whoever follows you of the believers.
لِلْفُقَرَاءِ الْمُهٰجِرِيْنَ الَّذِيْنَ أُخْرِجُوْا مِنْ دِيَارِهِمْ وَأَمْوَالِهِمْ يَبْتَغُوْنَ فَضْلًا مِّنَ اللَّهِ وَرِضْوَانًا وَّيَنْصُرُوْنَ اللَّهَ وَرَسُوْلَهُ أُولٰئِكَ هُمُ الصّٰدِقُوْنَ
For the poor emigrants who were expelled from their homes and their properties, seeking bounty from Allah and [His] approval and supporting Allah and His Messenger, [there is also a share]. Those are the truthful.
Allah says here that they are Sadiqun. Truthfulness, and more so when attested to by Allah, is a sign of them not being hypocrites.
Even if it was only for their emigration, their Jihad, their sacrificing their lives and wealth, their parents and children being killed, their well-wishing in din and strong iman and conviction, then these would have been a sufficient amount of virtue.
عن عبد الله بن مغفل قال قال رسول الله صلى الله عليه وسلم الله الله في أصحابي لا تتخذوهم غرضا بعدي فمن أحبهم فبحبي أحبهم ومن أبغضهم فببغضي أبغضهم ومن آذاهم فقد آذاني ومن آذاني فقد آذى الله ومن آذى الله فيوشك أن يأخذه
It has been reported by ‘Abdullah ibn Mughaffal radiya Llahu ‘anhu: The Rasul of Allah salla Llahu ‘alayhi wa sallam said, “Fear Allah when with regards to my Companions. Fear Allah when with regards to my Companions. Do not make them a target of abuse after me. He, who loves them, loves them because he loves me. He, who hates them, hates them because he hates me. He who harms them has harmed me, and he who harms me has harmed Allah, and he who harms Allah, then it is very soon that Allah will take him to task.
عن أبي هريرة قال: قال رسول الله صلى الله عليه وسلم لا تسبوا أصحابي لا تسبوا أصحابي فوالذي نفسي بيده لو أن أحدكم أنفق مثل أحد ذهبا ما أدرك مد أحدهم ولا نصيفه
It is narrated from Abu Hurairah radiya Llahu ‘anhu that the Rasul of Allah salla Llahu ‘alayhi wa sallam said, “Do not curse my Sahabah. Do not curse my Sahabah. By Allah, If anyone of you gives gold which is equivalent to the mountain of ‘Uhud in charity, it would not equal even a mudd or half a mudd of the reward they have attained (despite not giving so much).
3- It has been narrated with Tawatur from the Rasul of Allah salla Llahu ‘alayhi wa sallam that He said:
خير الناس قرني ثم الذين يلونهم…
The best of people are my generation, then those who are after my generation…
أخبرنا بهز عن أبيه عن جده قال سمعت نبي الله صلى الله عليه وسلم يقول ألا إنكم توفون سبعين أمة.أنتم خيرها وأكرمها على الله
The Rasul of Allah salla Llahu ‘alayhi wa sallam said, “Verily you complete seventy Ummahs and you are the best and most honoured in the eyes of Allah.
Based on the aforementioned verses and ahadith—and those not mentioned—the belief of the Muslims regarding the Companions of the Rasul of Allah salla Llahu ‘alayhi wa sallam is that they are the best of people after the Ambiya’.
Muslims also believe in the validity of the Khilafah of Abu Bakr radiya Llahu ‘anhu after the demise of Rasul Allah salla Llahu ‘alayhi wa sallam who was chosen by the Sahabah and thereafter in the Khilafah of ‘Umar radiya Llahu ‘anhu, who was appointed by Abu Bakr radiya Llahu ‘anhu. Thereafter in the Khilafah of ‘Uthman radiya Llahu ‘anhu who was elected by the consensus of the Shura and the entire Muslim community, as was advised by ‘Umar radiya Llahu ‘anhu. Thereafter in the Khilafah of ‘Ali Ibn ‘Abi Talib radiya Llahu ‘anhu unto whom the participants of Badr had pledged allegiance, viz. ‘Ammar ibn Yasir, Sahal ibn Hunayf, and the other Sahabah who followed suit.
Muslims also believe in the superiority of the Sahabah which is based on the following verses and others:
لَقَدْ رَضِيَ اللهُ عَنِ الْمُؤْمِنِينَ إِذْ يُبَايِعُونَكَ تَحْتَ الشَّجَرَةِ
Certainly was Allah pleased with the believers when they pledged allegiance to you, [O Muhammad], under the tree.
وَالسَّابِقُوْنَ الْأَوَّلُوْنَ مِنَ الْمُهَاجِرِيْنَ وَالْأَنصَارِ وَالَّذِيْنَ اتَّبَعُوْهُمْ بِإِحْسَانٍ رَّضِيَ اللَّهُ عَنْهُمْ وَرَضُوْا عَنْهُ
And the first forerunners [in the faith] among the Muhajirin and the Ansar and those who followed them with good conduct – Allah is pleased with them and they are pleased with Him.
Therefore it is not possible for a person who Allah has declared his love for, to do any action thereafter which will draw the anger of Allah. Allah did not declare His love for those after the Sahabah except if they follow the Sahabah with Ihsan. So, if any of the Tabi’in (those who succeeded the Sahabah) look down upon the Sahabah in any way, he will not be regarded as one who follows the Sahabah with Ihsan. So this particular person will not be part of the love which Allah has declared for this group.
There is an excellent answer given by Hassan al Basri when he was asked regarding the battles that took place between some of the Sahabah. He replied, “These were battles which the Sahabah took part in and we were not present therein, they understood the events that unfolded and we have not understood, they got together and we followed and they differed so we held back (our views and opinions).”
The pious predecessors have chosen not to delve into these discussions. They would say, “Allah has kept our hands pure from their blood therefore we will not stain our tongues by discussing it.”
We look at them as role models.
وَلَا تَجْعَلْ فِيْ قُلُوْبِنَا غِلًّا لِلَّذِيْنَ آمَنُوْا رَبَّنَا إِنَّكَ رَؤُوْفٌ رَحِيْمٌ
And put not in our hearts [any] resentment toward those who have believed. Our Lord, indeed You are Kind and Merciful.
 Al ‘Isabah, pg. 8
 Surah Al ‘Imran: 110
 Surah al Baqarah: 143
 Surah al Fath: 18
 Surah al Tawbah:100
 Surah al Anfal: 64
 Surah al Hashr: 8
 Sunan al Tirmidhi, #3862, Chapter regarding the person who curses the Sahabah radiya Llahu ‘anhum. Al Tirmidhi has declared it as: Hadith Gharib and some prints of the Sunan have the words Hassan Gharib. Gharib refers to a hadith which is narrated by a single narrator. This narration has also appeared in Sahih Ibn Hibban, #6256, However there is some weakness in the chain of narrators.
 Mudd: A measurement of volume equivalent to approximately 750ml.
 Sahih Muslim, # 2540, Book on the virtues of the Sahabah radiya Llahu ‘anhum, Chapter regarding the impermissibility of verbally abusing the Sahabah radiya Llahu ‘anhum.
 Tawatur refers to a report so authentically and abundantly narrated that it is impossible to deny.
 Sahih al Bukhari, #3450, Chapter on the virtues of the Sahabah; Sahih Muslim, # 2533, Book on the virtues of the Sahabah radiya Llahu ‘anhum, Chapter regarding virtues of the Sahabah radiya Llahu ‘anhum and then those after their generation.
Musnad Ahmed, #20041 Shu’ayb al ʾArnaʾut said, “The chain of narrators are Hassan (sound).”
 A consultative committee appointed by ‘Umar radiya Llahu ‘anhu comprising of six Sahabah to appoint the Khalifah from amongst themselves.
Surah al Fath: 18
Surah al Tawbah: 100
 Ihsan means the pursuit of excellence in worshiping Allah subhanahu wa ta ‘ala
 I’tiqad al A’immah al Hadith of Abu Bakar al ʾIsmaili, vol.1 pg.71; Lum’at al I’tiqad of Ibn Qudamah, vol.1 pg.171; Sharh al ‘Aqidah al Tahawiyyah of Ibn Abi al ‘Izz, vol.1 pg.485 (There are many other sources too).
‘Awn al Ma’bud, vol.12 pg.274
 Surah al Hashr: 10