Referring to the Prophet as (master)
What is the ruling on bestowing mastership (considering and calling them 'masters', Ar. Sayyid) upon the Prophet, Ahl ul-Bayt (members of the Prophet's household) and the righteous friends of Allah?
Muslims unanimously agree that the Prophet is the master of all creation. In conformity to this, he said, "I am the master of the progeny of Adam" and, "I am the master of the people" [Bukhari and Muslim]. Moreover, Allah the Almighty commanded us to respect and honor the Prophet and says,
We have truly sent thee as a witness, as a bringer of Glad Tidings, and as a Warner. In order that ye (O men) may believe in Allah and His Messenger, that ye may assist and honour Him, and celebrate His praise morning and evening. [Al-Fat-h, 8-9]
Bestowing mastership upon the Prophet
Qutada and As-Suddiy maintained that one of the means of venerating the Prophet is by bestowing mastership upon him. The Companions (may Allah be pleased with them) addressed him as 'master'; Sahl Ibn Hunaif (may Allah be pleased with him) said, "We passed by a mountain stream where I washed. I caught a fever and news of this reached the Prophetwho said, "Tell Abu Thabit to recite the last two chapters of the Qur`an." I said, "O my master! Is it permissible to recite ruqyah [Qur`anic recitation for protection]?" The Prophet replied, "The ruqyah is not permissible except [as a cure from] the evil eye, a fever or a [poisonous] sting".
The Companions likewise addressed the Prophetas 'master' when they invoked prayers and salutations upon him. Abduallah Ibn Mas`ud (may Allah be pleased with him) said, "When you invoke prayers and salutations upon the Messenger of Allah, perfect your invocation for it may be presented to him." They [the Companions] said, "Tell us how." He said, "Say, 'O Lord! Let Your prayers, mercy and salutations be upon the master of messengers, the leader of the pious, the seal of prophets, Muhammad Your slave and messenger, the leader of righteousness and messenger of mercy…".
Bestowing mastership upon other than the Prophet
Likewise, it is permissible to bestow mastership upon people other than the Prophet as is evidenced by primary texts and the practice of the early and latter generations from among the Islamic community without censure.
Allah the Almighty says about our master Yahya,
While he was standing in prayer in the chamber, the angels called unto him: "(Allah) doth give thee glad tidings of Yahya, confirming the truth of a Word from Allah, and (be besides) noble, chaste, and a Prophet, - of the (goodly) company of the righteous. [Al-'Imran, 39]
Imam Al-Qurtubi said, "This verse proves the permissibility of referring to a person as 'master'. It is also permissible to call him 'honorable' or 'noble'."
Allah the Almighty says about our master Yusuf and the
So they both raced each other to the door, and she tore his shirt from the back: they both found her lord near the door. She said: "What is the (fitting) punishment for one who formed an evil design against thy wife, but prison or a grievous chastisement? [Yusuf, 25]
The Prophet said about al-Hassan and al-Hussein (peace be upon them), "Al-Hassan and al-Hussein are the masters of the youths of Paradise." 
The Prophet said about al-Hassan Ibn 'Ali (peace be upon them), "This son of mine is a master" [Bukhari].
The Prophet asked Fatima (peace be upon her), "O Fatima! Do you not wish to be the mistress of believing women?" [Bukhari]
The Prophet ordered the Companions to stand up when Sa'd Ibn Mu'adh entered. He said, "Stand up before your master." [Bukhari]
The Prophet asked the tribe of Banu Salma, "Who is your master?" They replied, "Our master, Jad Ibn Qais, though we find him miserly." The Prophet said, "Nothing is worse than being a miser! Your master is 'Amr Ibn al-Jamuh."And in a different version of the report, the Prophetsaid, "Your master is Bishr Ibn al-Bara` Ibn Ma'rur."
The practice of the community
Referring to Abu Bakr Al-Siddiq and Bilal (may Allah be pleased with them), 'Umar al-Faruq said, "Abu Bakr is our master and he has manumitted our master" [Bukhari].
'Ali said about his son al-Hasan (may Allah be pleased with them both), "This son of mine is a master as he was thus called by the Prophet " [Abu Dawud].
Abu Huraira addressed Al-Hasan Ibn 'Ali (peace be upon them) and said, "O, my master!" He was told, "Do you say my master?!" He replied, "I heard the Prophet say, "He is a master."
The Companions witnessed the above reports and did not criticize or repudiate them, a fact which amounts to a tacit agreement and is thereby considered legal evidence as established by principles of Islamic law.
For ages, Muslims have been referring to the noble descendants of the masters of the youths of Paradise Al-Hasan and Al-Husein (peace be upon them) as 'masters'. In a non-prophetic tradition, 'Abduallah Ibn Mas'ud (may Allah be pleased with him) said, "Whatever Muslims regard as good is good before Allah and whatever they regard as evil is evil before Allah" [Ahmed].
Based on the above, it is lawful to bestow mastership upon Ahl ul-Bayt and the righteous friends of Allah. Rather, it is an expectation because it is a sign of respect and honor. The Prophet said, "He is not from us who does not acknowledge the honor due to our elders, who shows no mercy to our young and who does not recognize the right of our scholars." 
Recorded by Ahmed and al-Hakim who declared it authentic.
Recorded by Ibn Majah. Al-Mundhiri declared it fair. It was also reported through Abdullah Ibn 'Umar [may Allah be pleased with them both] as it was recorded by Ahmed Ibn Mani' in his Musnad with a sound transmission.
Recorded by al-Tirmidhi. Al-Hakim declared it fair.
Recorded by Bukhari in Adb Mufrad
Recorded by al-Tabarani in Al-Mu'jam Al-Kabir
Recorded by al-Nisa`i in 'Aml al-Youm wa al-Layla
Recorded by Ahmed. Al- Hakim declared it fair through 'Ibadah Ibn Samit [may Allah be pleased with him]