Who are the Poor on Judgement Day
Abu Huraira. reported Allah’s Messenger (may peace be upon him) as saying: Do you know who is poor? They (the Companions of the Holy Prophet) said: A poor man amongst us is one who has neither dirham with him nor wealth. He (the Holy Prophet) said: The poor of my Ummah would be he who would come on the Day of Resurrection with prayers and fasts and Zakat but (he would find himself bankrupt on that day as he would have exhausted his funds of virtues) since he hurled abuses upon others, brought calumny against others and unlawfully consumed the wealth of others and shed the blood of others and beat others, and his virtues would be credited to the account of one (who suffered at his hand). And if his good deeds fall short to clear the account, then his sins would be entered in (his account) and he would be thrown in the Hell-Fire.
Sahih Muslim Book 32, Number 6251:

May Allah guard us against Oppressing others, May Allah strengthen our Moral Character

Oppression is the darkness on the Day of Resurrection.
Jabir b. Abdullah reported that Allah’s Messenger (may peace be upon him) said: Be on your guard against committing oppression, for oppression is a darkness on the Day of Resurrection, and be on your guard against petty mindedness for petty mindedness destroyed those who were before you, as it incited them to shed blood and make lawful what was unlawful for them.
Sahih Muslim Book 32, Number 6248:

Ibu ‘Umar reported Allah’s Messenger (may peace be upon him) as saying: Oppression is the darkness on the Day of Resurrection.
Sahih Muslim Book 32, Number 6249:

Saving others from Oppression
Salim reported on the authority of his father that Allah’s Messenger (may peace be upon him) said: A Muslim is the brother of a fellow Muslim. He should neither commit oppression upon him nor ruin him, and he who meets the need of a brother, Allah would meet his needs, and he who relieved a Muslim from hardship Allah would relieve him from the hardships to which he would be put on the Day of Resurrection, and he who did not expose (the follies of a Muslim) Allah would conceal his follies on the Day of Resurrection.
Sahih Muslim Book 32, Number 6250: