Allah enjoins moderation in living. He condemns miserliness and forbids extravagance.
وَلاَ تَجْعَلْ يَدَكَ مَغْلُولَةً إِلَى عُنُقِكَ
(And let not your hand be tied (like a miser) to your neck,) this means, do not be miserly and stingy, never giving anything to anyone, as the Jews - may the curses of Allah be upon them - said, "Allah's Hand is tied up (i.e., He does not give and spend of His bounty)". They attributed miserliness to Him, Exalted and Sanctified be the Most Generous Bestower!
وَلاَ تَبْسُطْهَا كُلَّ الْبَسْطِ
(nor overextend it (like a spendthrift)) means, nor be extravagant in spending and giving more than you can afford, or paying more than you earn, lest you become blameworthy and find yourself in severe poverty. If you are a miser, people will blame you and condemn you, and no longer rely on you. When you spend more than you can afford, you will find yourself without anything to spend, so you will be worn out, like an animal that cannot walk, so it becomes weak and incapable. It is described as worn out, which is similar in meaning to exhausted. As Allah says:
Spending in the way of Allah so liberally as would throw one in trouble: The pros and cons of it
The verse, given the outer view, seems to prohibit the kind of spending following which the spender himself ends up becoming poor and needy, a prey of all sorts of hardships and anxieties. Tafsir authority, al-Qurtubi has said that this injunction covers the general condition of Muslims who would, after such spending, find the resulting hardships distressing and the whole thing would make them contrite over past give-outs and grieve about it. The word: مَّحْسُورًا (mahsura: empty-handed - 29) of the Holy Qur'an provides a hint in this direction. (As in Tafsir Mazhari) As for the people of high determination, who would not be emotionally disturbed by hardships that may come later and would still go on fulfilling rights of those who hold such rights, this restriction does not apply to them. This is the reason that it was the customary practice of the Holy Prophet ﷺ that he would not store anything for tomorrow.
What came today was spent out today. And there were occasions when he would remain hungry reaching the outer limits of having to tie a piece of rock against his stomach (to simulate the weight of food). Then there were many among the noble Sahabah who had spent their entire wealth and property in the way of Allah during the blessed period of the Holy Prophet ﷺ who did not categorically prohibit it nor did he blame them for it. This tells us that the prohibition contained in this verse is for those who cannot brave the hardships of poverty and hunger and they would start to rue after spending that they would have been better off if they had not spent in the way of Allah. If so, this attitude would nullify the good they had done in the past. Hence, the prohibition.
Poorly managed spending is prohibited
And the main thing in the verse is that it prohibits spending haphazardly in the sense that one would ignore what may happen in the near future and spend on the spot. The result is that comes tomorrow, other needy people show up or one is required to take care of a major religious exigency and he would, then, be in no position to help out. (Qurtubi) Or, he may be rendered equally incapable of fulfilling the rights of his family, something he is duty-bound to fulfill. (Mazhari) Explaining the words: مَلُومًا مَّحْسُورًا (reproached, empty-handed - 29), Tafsir Mazhari says that the first word: مَلُوم (malum) relates to the first condition, that is, miserliness - meaning if he were to hold back on giving out of miserliness, people would reproach him.' And the word: مَّحْسُورًا (mahsura) relates to some condition other than this - meaning that one should not exaggerate in spending to the extent that he himself becomes a pauper. If so, he will turn empty-handed, defeated and rueful.
Tazkirul Quran
Maulana Wahiduddin Khan
Islam favours moderation in all matters. According to Islam, the middle way, i.e. avoidance of extremes, is the best way. ‘The best of matters is their moderation.’ The same advice has been given in respect of expenditure. Man should not be so niggardly as to degrade himself in the eyes of others, but neither should he spend so much as to leave himself with nothing. It has been recorded in the traditions of the Prophet Muhammad, that one who adopts the way of moderation will not be a pauper. Lack of moderation with regard to wealth generally develops in a man because he loses sight of the fact that the Giver is God. It is He Who in His wisdom gives less to one and more to another. God’s dictum on this subject has been recorded in a divinely inspired tradition (hadith qudsi) of the Prophet Muhammad, ‘There are some among My servants for whom poverty is better, that is, too much of wealth will lead them astray. If I were to make them wealthy, their faith would suffer. And there are some among My servants for whom being wealthy is better. If I were to make them paupers, their faith would suffer.’
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.