The Quran

قُل أَرَأَيتُم ما أَنزَلَ اللَّهُ لَكُم مِن رِزقٍ فَجَعَلتُم مِنهُ حَرامًا وَحَلالًا قُل آللَّهُ أَذِنَ لَكُم ۖ أَم عَلَى اللَّهِ تَفتَرونَ

Muhammad Asad

Say: "Have you ever considered all the means of sustenance which God has bestowed upon you from on high¹ - and which you thereupon divide into 'things forbidden' and 'things lawful?"²Say: "Has God given you leave [to do this] - or do you, perchance, attribute your own guesswork to God?"

This connects with the statement, in verse 57, that the Qur'an offers to man a complete guidance towards the good life and spiritual fulfilment in this world, and happiness in the life to come. As already mentioned in surah 2, note 4, the term rizq connotes all that may be good and useful to man, be it of a physical nature (in the conventional sense of "means of sustenance") or belonging to the realm of the mind (like reason, knowledge, etc.) or of the spirit (like faith, kindness, patience, etc.). Thus, it applies exclusively to positive, beneficial means of sustenance, and never to things or phenomena which are morally reprehensible and/or physically or socially injurious.
Lit., "and thereupon you have made some of it forbidden (haram) and [some of it] lawful (halal)". The fact that it is God who "has bestowed upon you from on high" (anzala 'alaykum) i.e., has willed that man should make use of - all that can be qualified as rizq, automatically makes all its manifestations lawful (Zamakhshari). In accordance with the doctrine that everything which has not been expressly forbidden by the Qur'an or the explicit teachings of the Prophet is eo ipso lawful, this verse takes a clear-cut stand against all arbitrary prohibitions invented by man or artificially "deduced" from the Qur'an or the Prophet's sunnah (Manar XI, 409 f.; see also note 58 on verse 36 of this surah, as well as 5:101-102 and the corresponding notes). In its wider sense, the above verse relates to people who refuse to be guided by revelation and prefer to "follow nothing but conjecture" (verse 36).