The Gemara relates that R’ Chiya told his wife that if and when a poor person comes to their door, she should immediately bring him bread to eat — even before they had a chance to make requests. R’ Chiya explained to her that in reward for her diligence in this matter, other people would immediately bring their children bread, when the children became impoverished. R’ Chiya’s wife was astonished, and she responded to here husband: “Are you cursing me?” To which R’ Chiya replied that the reality is that poverty is like a wheel that rolls around the world, and would therefore inevitably affect their descendants at some time (see Yevamos 63a for something about the state of the relationship of R’ Chiya and his wife).
On the basis of this discussion, the Vilna Gaon (see Pninim MeShulchan HaGra to Ki Sisa 30:12) explained the trop (cantillation) on the word ונתנו — and they shall give — in the phrase: כִּי תִשָּׂא אֶת־רֹאשׁ בְּנֵֽי־יִשְׂרָאֵל לִפְקֻֽדֵיהֶם וְנָתְנוּ אִישׁ כֹּפֶר נַפְשׁוֹ לַֽיהוָֹה בִּפְקֹד אֹתָם — If you uplift the heads of the Jews according to their count, and they shall give, each person, the redemption of his soul to Hashem when they are counted. The trop is a kadma v’azla.
This trop is placed specifically on ונתנו , as this word is a palindrome - a word that reads the same forwards and backwards. This word comes to indicate that sometimes the giver or his children will be compelled to accept charity from the person to whom they once gave tzedakah themselves.
The allusion in the trop is in the literal meanings of kadma v’azla — “goes in early and then goes forth.” Thus, R’ Chiya told his wife something along these lines: “Give the poor person the bread as soon as possible, so that the merit will go forth and provide for your children.”
[See Baal HaTurim ad loc. who also notes the palindrome, but explains that it comes to teach us that if a person gives to tzedakah, he will receive the money back in some manner, and thus, in the final analysis, he does not suffer financially from giving itzedakah.