Up to 70,000 people are expected to pray and fast in support of Proposition 8 at the Q -- while opponents will stand in unity during a candlelight vigil on Saturday night.
The prayer event is called "The Call" and will take place from 10 a.m. to 10 p.m.
A group of Evangelical Christians organized the event, but some religious leaders in San Diego say they don't support it.
"Proposition 8 is discriminatory because it sets some people aside as a fundamental difference not to be treated equally and unconditionally," said "I do not believe the California constitution should be used to take away fundamental rights."
Those against Proposition 8 are invited to an interfaith service at St.Paul's Cathedral at 10 a.m. San Diego Mayor Jerry Sanders, who came out in support of same-sex marriage last year, will be handing our candles at a candlelight vigil in Hillcrest with his daughter Lisa at the San Diego Gay and Lesbian Center beginning at 8 p.m. Saturday.