(all passages cited from NRSV)

One might point to Isaiah 1:16-17:

Wash yourselves; make yourselves clean;
     remove the evil of your doings from before my eyes;
cease to do evil,
     learn to do good;
seek justice,
     rescue the oppressed,
defend the orphan,
     plead for the widow.

Or Deuteronomy 15:7, 11:

If there is among you anyone in need, a member of your community in any of your towns within the land that the LORD your God is giving you, do not be hard-hearted or tight-fisted toward your needy neighbor...
 
Since there will never cease to be some in need on the earth, I therefore command you, "Open your hand to the poor and needy neighbor in your land."

Passages like this, in which our care for the vulnerable is demanded by God without regard to the cost to ourselves, abound throughout scripture. Even if we interject the rational (and somewhat utilitarian) caveat that this cost must be a sustainable one for those of us asked to pay (otherwise, we all will become poor and without adequate provision!), we are nonetheless cautioned that concern for one's own finances in the face of need leads to God's displeasure. For example, Amos foresaw destruction for those members of society who had amassed fortunes and were now living their luxuriant lifestyles at the cost of the poor (Amos 4:1-2; see also the imprecations in 6:1-7):

Hear this word, you cows of Bashan
     who are on Mount Samaria,
who oppress the poor, who crush the needy,
     who say to their husbands, "Bring something to drink!"
The Lord GOD has sworn by his holiness:
     The time is surely coming upon you,
when they shall take you away with hooks,
     even the last of you with fishhooks.

Jeremiah aptly describes the oppressive "scoundrels" among the (already sinful enough) people of God, who have failed to live up to the divine expectation (Jeremiah 5:26-28):

For scoundrels are found among my people;
     they take over the goods of others.
Like fowlers they set a trap;
     they catch human beings.
Like a cage full of birds,
     their houses are full of treachery;
therefore they have become great and rich,
     they have grown fat and sleek.
They know no limits in deeds of wickedness;
     they do not judge with justice
the cause of the orphan, to make it prosper,
     and they do not defend the rights of the needy.

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