Indeed, unification of Allah (may He be Glorified and Exalted) and singling out Him with worship is the core of Islam and its main pillar. Without ascertaining the oneness of worship, man cannot be a Muslim and his actions cannot be acceptable because acceptance of actions is connected by showing sincerity to Allah (may He be Glorified and Exalted) and following the Prophet (peace be upon him). Tawhidul-Uluhiyyah (Allah's Exclusive Right to be worshipped) is connected with retribution and reckoning for which the divine scriptures were revealed, Messengers were sent, and swords were raised in Jihad.
The following are some of the Shari`ah texts which explain the value and importance of Tawhidul-Uluhiyyah in the life of man and its impact on him:
• The oneness of Allah is the main objectives of all messages of Allah. Allah (Glory be to Him) says: "And verily, We have sent among every Ummah (community, nation) a Messenger (proclaiming): "Worship Allâh (Alone), and avoid (or keep away from) Tâghût (all false deities i.e. do not worship Tâghût besides Allâh)."" [Surat An-Nahl: 36].
Allah says: "And We did not send any Messenger before you (O Muhammad peace be upon him) but We revealed to him (saying): Lâ ilâha illa Ana [none has the right to be worshipped but I (Allâh)], so worship Me (Alone and none else)." [Surat Al Anbiya': 25].
He also says: "He sends down the angels with the Rûh (revelation) of His Command to whom of His slaves He wills (saying): "Warn (mankind) that Lâ ilâha illâ Ana (none has the right to be worshipped but I), so fear Me (by abstaining from sins and evil deeds)." [Surat An-Nahl: 2].
Allah (Exalted be He) says: "And they were commanded not, but that they should worship Allâh, and worship none but Him Alone (abstaining from ascribing partners to Him), and perform As-Salât (Iqâmat-as-Salât) and give Zakât, and that is the right religion." [Surat Al Bayyinah: 5].
The proof from the Sunnah is the Hadith of Abu Hurayrah (may Allah be pleased with him) that the Prophet (peace be upon him) said: "The Prophets are paternal brothers; their mothers are different, but their religion is one."
All messages of Allah have agreed to that great principle which is monotheism despite their difference in legislations as Allah (may He be Exalted) says: "To each among you, We have prescribed a law and a clear way." [Surat Al Ma'idah: 48]. It indicates that their religion is one which is Islam that is the only religion accepted by Allah. Allah's Saying: "Truly, the religion with Allâh is Islâm." [Surat Al `Imran: 19].
And His Saying: "And whoever seeks a religion other than Islâm, it will never be accepted of him, and in the Hereafter he will be one of the losers." [Surat Al `Imran: 85]. So, all religions and doctrines other than Islam are false, and whoever dies while adopting a religion other than Islam, he shall be one of the Hell dwellers. Allah (may He be Exalted) says: "Verily, those who disbelieved, and died while they were disbelievers, the (whole) earth full of gold will not be accepted from anyone of them even if they offered it as a ransom. For them is a painful torment and they will have no helpers." [Surat Al `Imran: 91].
• Worshipping Allah alone is the greatest right which the creation should fulfill toward their Creator (may He be Glorified and Exalted). Allah (may He be Exalted) says: "And your Lord has decreed that you worship none but Him." [Surat Al Isra': 23].
Allah also says: "Worship Allâh and join none with Him (in worship)." [Surat An-Nisa': 36]. He also says: "Nay! But worship Allâh (Alone and none else), and be among the grateful." [Surat Az-Zumar: 66]. A Muslim repeats in one day more than 17 times Allah's Saying: "You (Alone) we worship, and You (Alone) we ask for help (for each and everything)." [Surat Al Fatihah: 5].
The greatest right is the right of Allah (may He be Exalted) to be worshipped and not associating with Him anyone in worship. It was reported in the Hadith of Mu`adh (may Allah be pleased with him) who said: "I was riding behind the Prophet (peace be upon him) and he called out: O Mu`adh! I said: Here I am at Your Service, and for Your Pleasure. Then the Prophet said the same thing three times and went on: Do you know what is Allah's Right on His Servants? I said: No. He said: The right of Allah on His Servants is to worship Him and not associate anything with Him. Then he rode on for an hour and said: O Mu`adh. I replied: Here I am at Your Service, and for Your Pleasure. He said: Do you know what is the right of the Servants upon Allah if they do that? Not to punish them." 
• As Tawhidul-Uluhiyyah is the main pillar of the religion, the opposite is polytheism which wastes actions and generates sins as Allah (may He be Exalted) says: "And indeed it has been revealed to you (O Muhammad peace be upon him), as it was to those (Allâh's Messengers) before you: If you join others in worship with Allâh, (then) surely (all) your deeds will be in vain, and you will certainly be among the losers. * Nay! But worship Allâh (Alone and none else), and be among the grateful." [Surat Az-Zumar: 65 - 66].
Whoever dies as an infidel, he shall reside in Hell forever. Allah (may He be Exalted) says: "Verily, Allâh forgives not (the sin of) setting up partners (in worship) with Him, but He forgives whom He wills sins other than that, and whoever sets up partners in worship with Allâh, has indeed strayed far away." [Surat An-Nisa': 116]. Hence, the most grievous sin and the major sin is associating others with Allah in worship because of the Hadith of `Abdullah in Mas`ud (may Allah be pleased with him) who said: "O Messenger of Allah, what is the greatest sin? He (the Messenger) (peace be upon him) said: That you set up a rival unto Allah though He Alone created you."
• Jihad was ordained for great objectives, one of them is to make the people worship their Creator and free them from worshipping other than Allah. However, if non-Muslims pay Al Jizyah (Tribute) in return of their protection, they shall be protected, but if they refuse to pay it, they shall be fought until they believe or give up. Ibn `Umar (may Allah be pleased with them) narrated that the Messenger of Allah (peace be upon him) said: "I have been ordered (by Allah) to fight the people till they say: None has the right to be worshipped but Allah, and whoever said it then he will save his life and property from me except on trespassing the law (rights and conditions for which he will be punished justly), and his accounts will be with Allah."
• The retribution in the Hereafter and the final destination of a person is connected by the volume of monotheism. Allah (Glory be to Him) says: "Say (O Muhammad peace be upon him): I am only a man like you. It has been revealed to me that your Ilâh (God) is One Ilâh (God - i.e. Allâh). So whoever hopes for the Meeting with his Lord, let him work righteousness and associate none as a partner in the worship of his Lord." [Surat Al Kahf: 110].
Of the Sunnah is the Hadith of Abu Dhar (may Allah be pleased with him) that the Prophet (peace be upon him) said: "Gabriel said to me: Whoever amongst your followers die without having worshipped others besides Allah, will enter Paradise (or will not enter the (Hell) Fire)." The Prophet (peace be upon him) asked. "Even if he has committed illegal sexual intercourse or theft?" He replied, "Even then." 
It was reported in the Hadith of `Utban ibn Malik Al Ansary (may Allah be pleased with him) that the Prophet (peace be upon him) said: "If anybody comes on the Day of Resurrection who has said: La ilaha illal-lah, sincerely, with the intention to win Allah's Pleasure, Allah will make the Hell-Fire forbidden for him." 
So, the oneness of Allah is the way of winning His Pleasure and Paradise, and saving oneself of His Wrath and Fire. Tawhidul-Uluhiyyah is the core of religion and its main pillar upon which the acts of worship, transactions, and manners are based. Children are the dear gem to their parents, the core of family and society, the hope, and the future. So, rearing them on pure monotheism is an educational basis as rearing is not valid without monotheism which is the basis of Islam.
 [Reported by Al Bukhari and Muslim]: Reported by Al Bukhari in the book of Prophets (3442) and Muslim in the book of virtues (2365).
 [Reported by Al Bukhari and Muslim]: Reported by Al Bukhari in the book of asking for permission (6267) with his own wordings, and Muslim in the book of faith (30).
 [Reported by Al Bukhari and Muslim]: Reported by Al Bukhari in the book of prescribed punishments (6811) and Muslim in the book of faith (86).
 [Reported by Al Bukhari and Muslim]: Reported by Al Bukhari in the book of faith (25) and Muslim in the book of faith (22).
 [Reported by Al Bukhari and Muslim] Reported by Al Bukhari in the book of the Beginning of creation (3222) and Muslim in the book of faith (94).
 [Reported by Al Bukhari and Muslim]: Reported by Al Bukhari (6422) and Muslim in the book of faith (33).
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