U'budū and ʿibāda are interpreted in three ways:
1. U'budū [worship], means to perform tawhid (the oneness of God); as in the following verses:
Worship Allah [aʿbudū] (that is, affirm His oneness); you have no deity other than Him. (al-Aʿrāf 7:59)
Ṣāliḥ also said the same things to his people.
Worship Allah [aʿbudū] (that is, perform tawhid), and do not associate anything with Him! (al-Nisāʾ 4:36)
Worship Allah [aʿbudū] (that is, affirm His oneness), and have taqwa (God-consciousness) of Him! (Nūḥ 71:3)
2. The phrase yaʿbudūna [they worship] is used in the sense of obeying; as in the following verses:
On that Day He will gather them all together and then say to the angels, "Was it you these people used to worship (that is, obey in matters of shirk)?" They will say, "Exalted are You! You are our Protector, not them. Rather, they worshipped the jinn (that is, by worshipping us, they were actually obeying the devils)." (Sabaʾ 34:40-41)
We disassociate ourselves from you. They did not worship us (that is, they did not obey us in matters of shirk). (al-Qaṣaṣ 28:63)
Did I not enjoin upon you, O children of Adam, that you not worship Satan (that is, do not obey him in matters of shirk)? (Yā Sīn 36:60)
3. Al-ʿibād means those under ownership [servants, slaves]; as in the following verses:
(Conveying from Me) say: "O My ʿibād (that is, those under My ownership [My slaves / servants]) who have transgressed against themselves..." (al-Zumar 39:53)
They made a portion for Him from among His ʿibād (that is, from those under His ownership [His slaves / servants]). (al-Zukhruf 43:15)
And from among your ʿibād (that is, from those under your ownership [your slaves]) the righteous... (al-Nūr 24:32)