WajaAAaloo lillahi mimma tharaa mina alharthi wal-anAAami naseeban faqaloo hatha lillahi bizaAAmihim (surah Anam: 136)

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(6:136) They *104 assign to Allah a portion out of the produce and cattle that He has created, saying out of their fancy: 'This is for Allah' - so they deem -'and this is for the associates (of Allah) whom we have contrived.' *105 Then, the portion assigned to the beings whom they have set up as associates (of Allah) does not reach Allah, but the portion assigned to Allah reaches the beings they set up as associates (of Allah)!  *106Indeed evil is what they decide!

Wa ja`aloo lillaahi mimmaa zara-a minal harsi walan`aami naseeban faqaaloo haazaa lillaahi biza`mihim wa haaza lishurakaa`inaa famaa kaana lishurakaaa`ihim falaa yasilu ilal laahi wa maa kaana lillaahi fahuwa yasilu ilaa shurakaaa`ihim; saaa`a maa yahkumoon

*104). There now follows an elucidation of the 'ignorance' which those people-insistently clung to, and which they were not prepared to forsake. They are also told about that major 'wrong' which, if not abandoned, will bar their way to salvation.
*105). They themselves acknowledged that the earth belongs to God, and that it is He Who causes the vegetation to grow. They also affirmed that God is the creator of the animals which were yoked to their service. They believed, however, that the grace of God for them was the outcome of the blessing and benediction of the angels, jinn, heavenly stars, spirits of their pious ancestors and so on, who cared for their well-being and were their patrons. They therefore used to make a two-fold division of their harvest and livestock offerings. One part was devoted to God in recognition of their gratitude to Him for having granted them farms and animals, while the rest was devoted to the household gods of either their family or tribes in order to ensure their continuing grace and benediction.
First, God censures them for this iniquity and asks them - since all those animals were created and had been granted to them by God alone - what justification there is for making offerings to others. Is it not sheer ingratitude to ascribe the acts of benevolence and grace of the true Benefactor to the intercession of others, and to associate them with God in thanksgiving? Second, they are censured indirectly for assigning quite an arbitrary share in their offerings to God, as if they themselves were the law-maker who could ascribe shares to God and others as they wished. To God alone belong all the bounties He has given man, and only His Law should therefore determine what part of those bounties should be offered to Him in thanksgiving and how the remaining should be spent. Hence even if they spend something in the way of Allah, for the poor and the deprived, but according to their own will, that does not deserve to be accepted by Him.
*106). This is subtle sarcasm at the trickery to which the polytheists resorted while dividing the offerings between God and the partners whom they had set up with Him. By one device and another they increased the share of the false deities, which only showed that their heart lay with those sham partners of God rather than with Him.
It is instructive to recall those tricks. If, while they were apportioning God's share of cereals and fruits, anything belonging to His share fell out of its place, it used to be added to the portion earmarked for the share of God's partners. On the contrary, if any part of the, partners' share fell out or got mixed up with the portion earmarked for God, they were most careful to return it to where it belonged. Whenever they were criticized for this, they had a number of interesting apologies to offer. They said, for instance, that being the Creator, God is Self-Sufficient and hence He does not care if His portion is in some way reduced. As for the 'partners', they were not after all self-sufficient and would therefore take them to task for the slightest diminution in their share.
In order to grasp what lay at the root of these superstitions, it is essential to know that the portion which these ignorant people earmarked for God was devoted to helping the indigent, the poor, travellers, orphans and so on. On the other hand, the portion earmarked for offerings to the partners' actually went either directly to the coffers of the priestly class or was offered at the shrines and thus ultimately reached the priests and caretakers of those shrines. Over the course of centuries these selfish religious leaders had impressed upon those simple-minded people that there was no harm in God's share being reduced, but that of God's dear ones, far from being diminished, should be increased.