Among the options you provided, several are significant teachings in Judaism, but the one that is often emphasized as a key teaching is "love your neighbor." This principle is derived from the Torah, specifically from Leviticus 19:18, which states, "You shall love your neighbor as yourself."
The other options also have important roles in Jewish teachings:
- Slavery is forbidden: While Judaism has specific laws regarding treatment of slaves, the overall movement towards justice and compassion in Jewish ethics leads to opposition to slavery in modern contexts.
- Do not make war: While Judaism does address the ethics of war, it's not as central as the teaching of loving one's neighbor.
- Righteousness: This is a significant concept in Judaism, particularly in the context of living a just and ethical life.
- Observe the Sabbath: Observance of the Sabbath (Shabbat) is a fundamental practice in Judaism, but it pertains more to ritual than to ethical teaching.
Overall, "love your neighbor" is a foundational ethical principle in Judaism.