The Good Deal
In his literary anthology al-Kashkūl, the Safavid polymath Shaykh Bahāʾī (d. 1629) says:
Regarding the verse “It is you we worship and you we ask for help,” commentators have mentioned several reasons why the plural “we” is used instead of the singular “I.” One of the best explanations is what al-Imām al-Rāzī said in al-Tafsīr al-kabīr. The gist of it is that in the sharia if someone sells several different things all at once and one of them turns out to be defective, the buyer can either return all of them or keep all of them, but he does not have the right to return the defective thing and keep the rest. For this reason, when a worshipper sees that his worship is defective, he does not present it to God; rather, he joins the worship of all worshippers—including prophets, saints, and the righteous—to his worship and presents it all at once with the hope that his worship will be accepted too. Because there is no doubt that some of it is acceptable, he can be sure the totality of worship will not be rejected. If God has forbidden us from returning what is defective and keeping the rest, how could he, in his magnanimity, do otherwise? Thus the use of the plural “we” ensures our defective worship is accepted alongside the worship of prophets, saints, and the righteous.