But those who wrong follow their [own] desires without knowledge. Then who can guide one whom Allāh has sent astray? And for them there are no helpers.
This is the parable Allah makes of the idolators, those who worship others besides Him and attribute partners to Him, while at the same time admitting that these so-called partners -- idols and false gods -- are enslaved to and belong to Him. In their Talbiyah (during Hajj and `Umrah they used to say, "At Your service, You have no partner except the partner that You have, You own Him and whatever he owns."
ضَرَبَ لَكُمْ مَّثَلاً مِّنْ أَنفُسِكُمْ
(He sets forth for you a parable from yourselves) `something which you yourselves can see witness, and understand.'
لَهُ الْمَثَلُ الْأَعْلَىٰ (For Him is the highest attribute - 30:27) The word مَثَل mathal is used for any such thing which has resemblance and similarity with something else, but its being exactly like that is not necessary. Therefore, the Qur'an has used the word 'mathal' for Allah Ta’ ala at several places, as in this very verse, and in another but Allah Ta’ ala's Being is completely beyond resemblance. (That is why the word 'mathal' has been translated above as 'attribute', which is also a possible lexical meaning of the word.)
Tazkirul Quran
Maulana Wahiduddin KhanOn ayahs 29–31
If there is common property, all those who share it have a right to it, and every partner has to think of the other partners. But, God’s position is not of this kind. God alone is the Lord of the entire Universe. The relation between God and His creatures is the same as that between master and servant on a larger scale, and not that of sharers of a property. Nobody gives his servant a status equal to that of himself. Similarly there is no one in the entire universe who enjoys a status equal to that of God. Lordship is for God, while for all other creatures there is only subjection. Apart from this, any other equation propounded will be based only on supposition and not on any real ground.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.