The gemara says on Daf 4 that if a non-Jew gives tzedaka on the condition that x should happen, that its looked down upon. However, if a Jew gives tzedakah on the condition that x should happen, he's considered virtuous.
Why is there a difference?
One pshat I heard is that when a non-Jew gives tzedakah on the condition that x should happen, but then x subsequently does not happen, the non-Jew fully regrets giving the tzedakah in the first place. On the other hand, a Jew won't regret giving the tzedakah even if x didn't happen.
To explain why a Jewish person giving tzedakah is virtuous, a pshat I heard is that poor people have a hard time accepting tzedakah. After all, "Soneh matanos yichyeh," one who hates presents will live long. So when a Jew gives tzedakah on the condition x happens, he's telling the poor person to accept the present, because by accepting the present, the poor person is really doing a favor for the giver.