The Meaning of Worship by Shaykh ’Abdur-Rahmân Ibn Hasan (d.1258H) 
The Meaning of Worship
The statement of Allâh – the Most High – : “I did not create the Jinn, nor mankind, except to worship Me.” [Sûratudh-Dhâriyât 51:56]
Shaykhul-Islâm Ibn Taymiyyah (d.728H) rahimahullâh – said: “Worship (al-’Ibâdah) is obedience to Allâh by following that which He ordered upon the tongues of His Messengers.” He also said, “Worship (al-’Ibâdah) is a comprehensive term covering everything that Allâh loves and is pleased with – whether saying, or actions, outward and inward.” 
Ibnul-Qayyim (d.751H) – rahimahullâh – said: “Worship revolves around fifteen principles. Whosoever completes them has completed the stages of ’ubûdiyyah (servitude to Allâh). The explanation of this is that ’ibâdah is divided between the heart, the tongue, and the limbs. And that for each one of these three come five types of rulings, covering all actions: wâjib (obligatory), mustahabb (recommended), harâm (prohibited), makrûh (disliked), and mubâh (permissible).” 
Imâm al-Qurtubî (d.671H) – rahimahullâh – said: “The root of ’ibâdah is humility and submissiveness. The various duties that have been prescribed upon the people are called ’ibâdât (acts of worship), since what is required is that these acts of worship must be done with humility and submissiveness to Allâh – the Most High.” 
Ibn Kathîr (d.774H) – rahimahullâh – said: “And ’ibâdah is obedience to Allâh by acting upon what He commands, and abandoning what He forbids; and this is the reality and essence of Islâm. And the meaning of Islâm is: istislâm (submission and surrender) to Allâh – the Most High – along with the utmost compliance, humility, and submissiveness to Him.”
He also said whilst explaining the above âyah: “Indeed Allâh – the Most High – created the creation so that they could worship Him alone, without associating any partner with Him. Whoever obeys Him will be completely rewarded, whereas whoever disobeys Him would be punished with a severe punishment. And He has informed that He is neither dependant, nor does He have any need for them. Rather, it is they who are in dire need of Him, in every condition and circumstance, since He is the One who created, sustains, and provides for them.” 
The Meaning of Tâghût
The statement of Allâh – the Most High – : “And to every nation We sent Messengers, ordering them that they should worship Allâh alone, obey Him, and make their worship purely for Him; and that they should avoid at-Tâghût.” [Sûratun-Nahl 16:36]
And at-tâghût is from the word at-tughyân, which means: going beyond the limits.
’Umar Ibnul-Khattâb radiallâhu ’anhu said: “The tâghût is Shaytân.” 
Jâbir radiallâhu ’anhu said: “The tâghûts are the soothsayers and fortune-tellers upon whom the devils descend.” 
Imâm Mâlik (d.179H) – rahimahullâh – said: “Tâghût is that which is worshipped besides Allâh.” 
So this is what has been mentioned by certain people. However, Imâm Ibnul-Qayyim – rahimahullâhu ta’âlâ – has given a very comprehensive definition, so he said, “The tâghût is all that which causes the person to exceed the limits with regards to that which is worshipped, followed, or obeyed. So the tâghût in any nation is whosoever turns to other than Allâh and His Messenger for matters of judgement; or is pleased to be worshipped besides Allâh; or is followed without a clear proof from Allâh; or is obeyed in that which is known to be disobedience to Allâh.” 
1. Fathul-Majîd li-Sharh Kitâbit-Tawhîd (1/84-90)
2. Majmû’ul-Fatâwâ (10/149) of Ibn Taymiyyah.
3. Madârijus-Sâlikîn (1/109)
4. Al-Jâmi’ li-Ahkâmil-Qur‘ân (1/225), and (17/56) of al-Qurtubî.
5. Tafsîrul-Qur‘ânil-’Adthîm (7/402)
6. Related by at-Tabarî in Jâmi’ul-Bayân ’an-Ta‘wîlil-Qur‘ân (no. 5834), al-Hâfidh Ibn Hajar said in Fathul-Bârî (8/251), “Its chain of narrators is strong.”
7. Related by at-Tabarî in his Tafsîr (no. 5845)
8. Related by as-Suyûtî in ad-Durarul-Manthûr (2/22), by way of Ibn Abî Hâtim.
9. I’lâmul-Muwaqqi’în (1/53)