This excerpt is taken from Sheikh Muhammad Iqbal Kilani's book "Al-Wala Wal-Bara" .
معني الولاء
"Wala" means love, friendship, kinship, support, assistance, and guardianship, etc. [اَللّٰہُ وَلِیُّ الَّذِیۡنَ اٰمَنُوۡا ۙ یُخۡرِجُہُمۡ مِّنَ الظُّلُمٰتِ اِلَی النُّوۡرِ۬ؕ وَ الَّذِیۡنَ کَفَرُوۡۤا اَوۡلِیٰٓـُٔہُمُ الطَّاغُوۡتُ ۙ یُخۡرِجُوۡنَہُمۡ مِّنَ النُّوۡرِ اِلَی الظُّلُمٰتِ ؕ] Allah is the friend of the believers; He brings them out of the darkness of disbelief into the light (of Islam), and those who disbelieve have as their friends the Taghut (false deities), who bring them out of the light into darkness.
Reference: (Surah Al-Baqarah:257)
❀ [وَ لَئِنِ اتَّبَعۡتَ اَہۡوَآءَہُمۡ بَعۡدَ مَا جَآءَکَ مِنَ الۡعِلۡمِ ۙ مَا لَکَ مِنَ اللّٰہِ مِنۡ وَّلِیٍّ وَّ لَا وَاقٍ] After knowledge (revelation) has come to you, if you follow the desires of the people, then you will have no protector or helper against Allah.
Reference: (Surah Ar-Ra'd:37)
❀ [وَ الَّذِیۡنَ اٰمَنُوۡا وَ لَمۡ یُہَاجِرُوۡا مَا لَکُمۡ مِّنۡ وَّلَایَتِہِمۡ مِّنۡ شَیۡءٍ حَتّٰی یُہَاجِرُوۡا ۚ] Those who believe but do not emigrate, you have no guardianship (i.e., inheritance) over them until they emigrate to you.
Reference: (Surah Al-Anfal:72)
من یستحق الولاء؟
Only Allah, Allah's Messenger (peace be upon him), and all the believers deserve the love and friendship of Muslims.
[اِنَّمَا وَلِیُّکُمُ اللّٰہُ وَ رَسُوۡلُہٗ وَ الَّذِیۡنَ اٰمَنُوا الَّذِیۡنَ یُقِیۡمُوۡنَ الصَّلٰوۃَ وَ یُؤۡتُوۡنَ الزَّکٰوۃَ وَ ہُمۡ رٰکِعُوۡنَ]،[وَ مَنۡ یَّتَوَلَّ اللّٰہَ وَ رَسُوۡلَہٗ وَ الَّذِیۡنَ اٰمَنُوۡا فَاِنَّ حِزۡبَ اللّٰہِ ہُمُ الۡغٰلِبُوۡنَ]
Indeed, your allies are none but Allah, His Messenger, and those who have believed - those who establish prayer and give zakah, and they bow [in worship]. And whoever is an ally of Allah and His Messenger and those who have believed - indeed, the party of Allah will be the predominant.
Reference: (Surah Al-Ma'idah:55-56)
أہمیـــۃ الولاء
Friendship changes a person's religion.
[عن ابی ہریرۃ رضی اللٰه عنہ قال: قال رسول اللٰہ صلی اللٰه علیہ وسلم، ألرجل علٰی دین خلیلہٖ فلینظر احدکم من یخالل]
Sayyiduna Abu Hurairah (may Allah be pleased with him) says the Messenger of Allah (peace be upon him) said: A man is upon the religion of his friend, so each one of you should consider whom he makes his friend.
Reference: Sunan At-Tirmidhi:2378
Good or bad friendship affects a person's beliefs and actions.
[عن أبي موسى رضي الله عنه، عن النبي صلى الله عليه وسلم، قال: مثل الجليس الصالح، والسوء، كحامل المسك، ونافخ الكير، فحامل المسك إما أن يحذيك، وإما أن تبتاع منه، وإما أن تجد منه ريحا طيبة، ونافخ الكير إما أن يحرق ثيابك، وإما أن تجد ريحا خبيثة]
It is narrated from Sayyiduna Abu Musa رضي الله عنه that the Messenger of Allah صلی اللہ علیہ وسلم said: The example of a good and bad friend is like that of a musk seller and a blacksmith who blows the fire in the furnace. If you befriend the musk seller, he will give you a gift of musk or you will buy musk from him yourself; if he does not give a gift and you do not buy it yourself, at least by sitting with him you will continue to enjoy the pleasant fragrance. But if you sit by the blacksmith at the furnace, the sparks of fire will burn your clothes, and if your clothes do not burn, the smoke from the furnace will certainly trouble your nose.
Reference: Sahih al-Bukhari:5534
Friendship also affects a person's outcome.
[عن انس رضي اللٰه عنه قال: قال رسول اللٰہ صلی اللٰه علیہ وسلم، أنت مع من أحببت]
Sayyiduna Anas رضي الله عنه says the Messenger of Allah صلی اللہ علیہ وسلم said: (On the Day of Judgment) you will be with those whom you loved.
Reference: Sahih Muslim:2639
On the Day of Judgment, only the friendship of righteous people will benefit.
[اَلۡاَخِلَّآءُ یَوۡمَئِذٍۭ بَعۡضُہُمۡ لِبَعۡضٍ عَدُوٌّ اِلَّا الۡمُتَّقِیۡنَ]
On the Day of Judgment, except for the pious, all friends will become enemies to each other.
Reference: (Surah Az-Zukhruf:67)
The people of faith should only befriend believers and pious people.
[عن أبي سعيد، أنه سمع رسول الله صلى الله عليه وسلم يقول: لا تصاحب إلا مؤمنا، ولا يأكل طعامك إلا تقي]
It is narrated from Sayyiduna Abu Saeed رضي الله عنه that he heard the Messenger of Allah صلی اللہ علیہ وسلم say: Do not make anyone your friend except a believer, and your food should only be eaten by a pious person.
Reference: Sunan At-Tirmidhi:2395
The Prophet Muhammad صلی اللہ علیہ وسلم taught to seek refuge from bad friends.
[عن عقبة بن عامر قال: كان رسول الله صلى الله عليه وسلم يقول: «اللهم إني أعوذ بك من يوم السوء، ومن ليلة السوء، ومن ساعة السوء، ومن صاحب السوء، ومن جار السوء في دار المقامة]
Sayyiduna Uqbah bin Amir رضي الله عنه says that the Prophet Muhammad صلی اللہ علیہ وسلم used to supplicate: O Allah! I seek Your refuge in my house from bad days and nights, bad times, bad friends, and bad neighbors.
Reference: Al-Mu'jam Al-Kabir by At-Tabarani: Vol 17, p.294, Hadith No:810