Some Acts of Shirk
Allah chastises and criticizes the idolators who invented innovations, Kufr and Shirk, and called on partners and rivals with Allah among His creation, although He created every thing, all praise is due to Him. This is why Allah said,
وَجَعَلُواْ لِلَّهِ مِمَّا ذَرَأَ
(And they assign to Allah from that which He has created,)
مِنَ الْحَرْثِ
(of the tilth) meaning, fruits and produce,
وَالاٌّنْعَامِ نَصِيباً
(and of the cattle a share) meaning a part and a section.
فَقَالُواْ هَـذَا لِلَّهِ بِزَعْمِهِمْ وَهَـذَا لِشُرَكَآئِنَا
(and they say: "This is for Allah," according to their claim, "and this is for our partners.") Allah said next,
فَمَا كَانَ لِشُرَكَآئِهِمْ فَلاَ يَصِلُ إِلَى اللَّهِ وَمَا كَانَ لِلَّهِ فَهُوَ يَصِلُ إِلَى شُرَكَآئِهِمْ
(But the share of their "partners" reaches not Allah, while the share of Allah reaches their "partners"!) `Ali bin Abi Talhah and Al-`Awfi narrated that Ibn `Abbas said; "When they, the enemies of Allah, would cultivate the land or collect produce, they would assign a part of it to Allah and another part to the idol. They would keep the share for the idol, whether land, produce or anything else, and preserve its division to such an extent that they would collect anything that accidentally falls from the share they assigned to Allah and add it to the share of the idol. If the water that they assigned for the idol irrigated something (a section of land, for instance) that they assigned for Allah, they would add whatever this water irrigated to the idol's share! If the land or produce that they assigned for Allah was accidentally mixed with the share that they assigned for the idol, they would say that the idol is poor. Therefore, they would add it to the share they assigned for the idol and would not return it to the share they assigned for Allah. If the water that they assigned for Allah irrigated what they assigned for the idol they would leave it (the produce) for the idol. They also made some of their other property sacred, like the Bahirah, Sa'ibah, Wasilah and Ham, assigning them to the idols, claiming that they do so as way of seeking a means of approach to Allah. Allah said,
وَجَعَلُواْ لِلَّهِ مِمَّا ذَرَأَ مِنَ الْحَرْثِ وَالاٌّنْعَامِ نَصِيباً
(And they assign to Allah a share of the tilth and cattle which He has created...)." Similar was said by Mujahid, Qatadah, As-Suddi and others. `Abdur-Rahman bin Zayd bin Aslam commented; "Every type of slaughter that they would assign for Allah, would never be eaten unless they mentioned the names of their idols when slaughtering it. Yet for what they sacrificed in the names of the idols, they would not mention Allah's Name when slaughtering it." He then recited the Ayah (6:136) until he reached,
سَآءَ مَا يَحْكُمُونَ
(Evil is the way they judge!) This Ayah means, evil is that which they determined, for they committed error in the division. Certainly, Allah is the Lord, Owner and Creator of all things and His is the dominion. All things are His property and under His supreme control, will and decree. There is no deity worthy of worship, or Lord, except Him. And even when the polytheists made this evil division, they did not preserve it, but cheated in it. Allah said in other Ayat,
وَيَجْعَلُونَ لِلَّهِ الْبَنَـتِ سُبْحَانَهُ وَلَهُمْ مَّا يَشْتَهُونَ
(And they assign daughters unto Allah -- glory be to Him -- and unto themselves what they desire.) 16:57, and
وَجَعَلُواْ لَهُ مِنْ عِبَادِهِ جُزْءًا إِنَّ الإنسَـنَ لَكَفُورٌ مُّبِينٌ
(Yet, they assign to some of His servants a share with Him. Verily, man is indeed a manifest ingrate!) 43:15, and,
أَلَكُمُ الذَّكَرُ وَلَهُ الاٍّنثَى - تِلْكَ إِذاً قِسْمَةٌ ضِيزَى
(Is it for you the males and for Him the females That indeed is a division most unfair!) 53:21-22.
Tafsir Ibn Kathir (abridged, English).