Is it against Judaism to donate to charity?

Quite the contrary, it’s a mitzvah (command) called Tzedakah.

"Tzedakah and acts of kindness are the equivalent of all the mitzvot of the Torah" – Jerusalem Talmud, Pe'ah 1:1.

"Greater is tzedakah than all the sacrifices" – Talmud, Sukkah 49b.

"If only the people who lived in the generation of the Flood and the people of Sodom had given tzedakah, they would not have perished" – Midrash Zutta, Song of Songs 1.

"Great is tzedakah, for since the day that the world was created until this day the world stands upon tzedakah" – Midrash Tanna d'Vei Eliyahu Zutta 1.

It is a mitzvah (blessing ) to donate to charity