Tawheed of Worship means that all acts of worship/ Ibadat belong to Allah alone, and for no one else.The biggest caller of Tawheed was our Prophet Muhammad Sallallahu Alaihi Wasallam.
Prophet taught us that All acts of worship are purely and sincerely for Allah, not for idols, Not to any power, not to bow for any one of any status weather Prophet or Aulia Allah. Sahaba asked Permission to do Sajda for beloved Prophet but Prophet forbade. So worship will not for the universe, not for anything except the one Allah.
Some Other cholars has divided into three categories.
That is Allah, your Lord! there is no god but He, the Creator of all things: then worship ye Him: and He hath power to dispose of all affairs. (6:102)
To Allah do belong the unseen (secrets) of the heavens and the earth, and to Him goeth back every affair (for decision): then worship Him, and put thy trust in Him: and thy Lord is not unmindful of aught that ye do. (11:123)
Verily your Lord is Allah, who created the heavens and the earth in six days, and is firmly established on the throne (of authority), regulating and governing all things. No intercessor (can plead with Him) except after His leave (hath been obtained). This is Allah your Lord; Him therefore serve ye: will ye not receive admonition? (10:3)
He has created the heavens and the earth for just ends: Far is He above having the partners (in worship) they ascribe to Him! (16:3)
He is the Living (One): There is no god but He: Call upon Him, giving Him sincere devotion. Praise be to Allah, Lord of the Worlds! (40:65)
Not a messenger did We send before thee without this inspiration sent by Us to him: that there is no god but I; therefore worship and serve Me. (21:25)
We sent Noah to his people. He said: "O my people! worship Allah! ye have no other god but Him. I fear for you the punishment of a dreadful day! (7:59)
But said Christ: "O Children of Israel! worship Allah, my Lord and your Lord." Whoever joins other gods with Allah,- Allah will forbid him the garden, and the Fire will be his abode. There will for the wrong-doers be no one to help. (5:72)
There is for you an excellent example (to follow) in Abraham and those with him, when they said to their people: "We are clear of you and of whatever ye worship besides Allah: we have rejected you, and there has arisen, between us and you, enmity and hatred for ever,- unless ye believe in Allah and Him alone (60:4)
And I have not created the jinn and the men except that they should serve Me. (51:56)
Say: "Who is it that sustains you (in life) from the sky and from the earth? or who is it that has power over hearing and sight? And who is it that brings out the living from the dead and the dead from the living? and who is it that rules and regulates all affairs?" They will soon say, "Allah". Say, "will ye not then show piety (to Him)?" (10:31)
Is it not to Allah that sincere devotion is due? But those who take for protectors other than Allah (say): "We only serve them in order that they may bring us nearer to Allah." Truly Allah will judge between them in that wherein they differ. But Allah guides not such as are false and ungrateful. (39:3)
Say: "Truly, my prayer and my service of sacrifice, my life and my death, are (all) for Allah, the Cherisher of the Worlds (6:162)
While they call on their Lord, in Fear and Hope (32:16)
When ye sought help of your Lord and He answered you (saying): I will help you with a thousand of the angels, rank on rank. (8:9)
And make not Allah's (name) an excuse in your oaths against doing good, or acting rightly, or making peace between persons; for Allah is One Who heareth and knoweth all things. (2:224)
The Prophet said, "If anybody has to take an oath, he should swear only by Allah." The people of Quraish used to swear by their fathers, but the Prophet said, "Do not swear by your fathers." (Sahih al-Bukhari, Volume 5, Book 58, Number 177)
"I put my trust in Allah, My Lord and your Lord! There is not a moving creature, but He hath grasp of its fore-lock. Verily, it is my Lord that is on a straight Path. (11:56)
"Verily, I am Allah: There is no god but I: So serve thou Me (only), and establish regular prayer for celebrating My praise. (20:14)
(Further, We sent a long line of prophets for your instruction). We sent Noah to his people: He said, "O my people! worship Allah! Ye have no other god but Him. Will ye not fear (Him)?" (23:23)
Behold, the messengers came to them, from before them and behind them, (preaching): "Serve none but Allah (41:14)
And (We also saved) Abraham: behold, he said to his people, "Serve Allah and fear Him: that will be best for you- If ye understand! "For ye do worship idols besides Allah, and ye invent falsehood. The things that ye worship besides Allah have no power to give you sustenance: then seek ye sustenance from Allah, serve Him, and be grateful to Him: to Him will be your return. (29:16-17)
"And the places of worship are for Allah (alone): So invoke not any one along with Allah
Narrated Mu'adh bin Jabal:
While I was riding behind the Prophet as a companion rider and there was nothing between me and him except the back of the saddle, he said, "O Mu'adh!" I replied, "Labbaik O Allah's Apostle! And Sa'diak!" He proceeded for a while and then said, "O Mu'adh!" I said, "Labbaik and Sa'daik, O Allah's Apostle!" He then proceeded for another while and said, "O Mu'adh bin Jabal!" I replied, "Labbaik, O Allah's Apostle, and Sa'daik!" He said, "Do you know what is Allah's right on His slaves?" I replied, "Allah and His Apostle know better." He said, "Allah's right on his slaves is that they should worship Him and not worship anything besides Him." He then proceeded for a while, and again said, "O Mu'adh bin Jabal!" I replied. "Labbaik, O Allah's Apostle, and Sa'daik." He said, "Do you know what is (Allah's) slaves' (people's) right on Allah if they did that?" I replied, "Allah and His Apostle know better." He said, "The right of (Allah's) slaves on Allah is that He should not punish them (if they did that)."