Islam has emphasized helping the poor and warns those who are careless about them of having a bad fate. Needless to say, helping the poor will be considered a good deed and will be rewarded if it were for the sake of God not an act of showing off or for achieving mundane goals.
Carelessness about the poor
Regarding those who have the financial means but do not help the poor, Imam Sadiq (as) said:
"Cursed, Cursed be the one to whom God bestowed wealth but he gave nothing of it to charity".
Helping the poor is a duty of the rich and will bring awful consequences if neglected. The Prophet of God (PBUH) described the generosity of man as a shade that will safeguard him from the torment of the hereafter. He said:
"The ground of the Day of Judgment will be fire except (under) the shade (which is) for the faithful person; verily his charity will cast shadow over him".
Carelessness about the poor, cause for ending up in Hell
The Quran in surah Muddathir, when enumerating the causes of ending up in Hell, counts not praying and not helping the poor as two reasons that will drive one to the fire of Hell. It quotes the residents of Paradise asking the residents of Hell:
مَا سَلَكَكُمْ فِي سَقَرَ قَالُوا لَمْ نَكُ مِنَ الْمُصَلِّينَ وَلَمْ نَكُ نُطْعِمُ الْمِسْكِينَ
"What put you into Saqar?" They will say, "We were not of those who prayed, Nor did we used to feed the poor.
Those who are rich but don't want to give money to charity usually make an excuse saying that God wanted the poor to be in poverty:
وَإِذَا قِيلَ لَهُمْ أَنفِقُوا مِمَّا رَزَقَكُمُ اللَّـهُ قَالَ الَّذِينَ كَفَرُوا لِلَّذِينَ آمَنُوا أَنُطْعِمُ مَن لَّوْ يَشَاءُ اللَّـهُ أَطْعَمَههُ إِنْ أَنتُمْ إِلَّا فِي ضَلَالٍ مُّبِينٍ
And when it is said to them, "Spend from that which Allah has provided for you," those who disbelieve say to those who believe, "Should we feed one whom, if Allah had willed, He would have fed? You are not but in clear error."
The Quran in surah Muddathir, when enumerating the causes of ending up in Hell, counts not praying and not helping the poor as two reasons that will drive one to the fire of Hell.
It is the nature of man to be driven into ignorance and ingratitude and acquire a feeling of self-sufficiency if he thinks that his wealth is the result of his own capabilities not the bounty of God:
كَلَّا إِنَّ الْإِنسَانَ لَيَطْغَىٰ أَن رَّآهُ اسْتَغْنَىٰ
"No! [But] indeed, man transgresses. Because he sees himself self-sufficient."
Qarun who lived at the time of Prophet Moses was such a person. He was a wealthy man but he did not care about the poor. He was told:
وَابْتَغِ فِيمَا آتَاكَ اللَّـهُ الدَّارَ الْآخِرَةَ وَلَا تَنسَ نَصِيبَكَ مِنَ الدُّنْيَا وَأَحْسِن كَمَا أَحْسَنَ اللَّـهُ إِلَيْكَ وَلَا تَبْغِغِ الْفَسَادَ فِي الْأَرْضِ إِنَّ اللَّـهَ لَا يُحِبُّ الْمُفْسِدِينَ
"But seek, through that which Allah has given you, the home of the Hereafter; and [yet], do not forget your share of the world. And do good as Allah has done good to you. And desire not corruption in the land. Indeed, Allah does not like corrupters."
But he did not pay attention to their advice. The Quran tells us about his unfortunate fate. He and his wealth were swallowed by the earth:
فَخَسَفْنَا بِهِ وَبِدَارِهِ الْأَرْضَ فَمَا كَانَ لَهُ مِن فِئَةٍ يَنصُرُونَهُ مِن دُونِ اللَّـهِ وَمَا كَانَ مِنَ الْمُنتَصِرِينَ
And We caused the earth to swallow him and his home. And there was for him no company to aid him other than Allah, nor was he of those who [could] defend themselves.
 Bihar al-Anwar, Vol. 93, p. 133, مَلْعُونٌ مَلْعُونٌ مَنْ وَهَبَ اللَّهُ لَهُ مَالًا فَلَمْ يَتَصَدَّقْ مِنْهُ بِشَيْء.
 Kafi, Vol.4, p. 3, أَرْضُ الْقِيَامَةِ نَارٌ مَا خَلَا ظِلَّ الْمُؤْمِنِ فَإِنَّ صَدَقَتَهُ تُظِلُّه.