The state Senate voted 25-22 for the law. The vote comes less than a week after the House of Delegates barely passed the measure.

Maryland will become the eighth state to allow gay marriage when O'Malley — who sponsored the bill — signs the legislation. The Democrat made the measure a priority this session after it stalled last year.

"This issue has taken a lot of energy, as well it should, and I'm very proud of the House of Delegates and also the Senate for resolving this issue on the side of human dignity, and I look forward to signing the bill," O'Malley said in a brief interview after the Senate vote.

Opponents, though, have vowed to bring the measure to referendum in November. They will need to gather at least 55,726 valid signatures of Maryland voters to put it on the ballot and can begin collecting names now that the bill has passed both chambers.

Some churches and clergy members have spoken out against the bill, saying it threatens religious freedoms and violates their tradition of defining marriage as between a man and a woman.

"The enormous public outcry that this legislation has generated — voiced by Marylanders that span political, racial, social and religious backgrounds — demonstrates a clear need to take this issue to a vote of the people," Maryland Catholic Conference spokeswoman Kathy Dempsey said in a statement. "Every time this issue has been brought to a statewide vote, the people have upheld traditional marriage."

"There remains a lot of work to do between now and November to make marriage equality a reality in Maryland," Joe Solmonese, HRC president said in a statement released Thursday. "Along with coalition partners, we look forward to educating and engaging voters about what this bill does: It strengthens all Maryland families and protects religious liberty."Leaders at the Human Rights Campaign, a group that joined a coalition of organizations to advocate for the bill, said they expect opponents will gather the required number of signatures.

Senators rejected some amendments to the legislation Thursday. Proponents warned that amending the bill could kill it because gathering enough support for altered legislation in the House would be difficult.

Last year senators passed a similar measure by 25-21, but the bill died in the House after delegates rescinded their initial support citing concerns that it could violate religious liberties of churches and business owners who do not support same-sex unions.

Sen. Allan Kittleman, the only Senate Republican to vote in favor of the legislation, said he is proud of his decision and not concerned about political consequences down the road.

"You don't worry about politics when you're dealing with the civil rights issue of your generation," said Kittleman, R-Howard, the son of the late Sen. Robert Kittleman, who was known for civil rights advocacy.

Christy and Marie Neff, who married in Washington, D.C., where same-sex marriage has been legal since 2010, stood outside the Senate chamber Thursday evening as crowds surrounded O'Malley and other key supporters.

The couple, who lives in Annapolis, has lobbied lawmakers to support the bill in recent years.

"This is our victory and we're going to savor this because you can only really jump one hurdle at a time," Christy Neff said. "So we're going to savor this and then if they bring it to referendum, we'll match that effort with the same sort of effort we did today."

Source: ABC News

After courting the votes of a couple delegates initially opposed to the measure, House members voted 72-67 to pass the bill. An initial vote count suggested the measure passed with 71 votes, leaving out an affirmative from Delegate John Bohanan.

Next up is the Senate, which handily passed a similar bill last year. Gov. Martin O'Malley sponsored the bill and has pushed for gay marriage to be legalized. Approval would make Maryland the eighth state plus the District of Columbia to legalize the marriages, although opponents have vowed to petition the measure to referendum.

"Today, we took a giant step toward marriage equality becoming law — and we are in this position due to the unwavering leadership and resolve of Governor O'Malley, Speaker (Michael) Busch and our legislative allies," Joe Solmonese, president of the Human Rights Campaign, said in a statement released Friday.

An amendment from Delegate Tiffany Alston, a Prince George's Democrat who previously opposed to the bill, was accepted by the members, a move opponents suggested secured her vote. It would keep the law from going into effect until any litigation related to a potential voters' referendum on the measure is processed.

The body also added an amendment Thursday evening, altering the effective date from October to January 2013.

Delegate Wade Kach, a Republican from Baltimore County, said earlier in that day that his support was contingent upon that amendment.

Throughout the week, several key lawmakers, including Kach and Republican Delegate Robert Costa, made pronouncements that after personal consideration they would support the legislation.

Opponents say the bill does not adequately protect religious freedoms and would force educators to teach about gay marriage in public schools.

Delegates rejected amendments to create civil unions, allow parents to opt out of education programs that address same-sex relationships, limit marriage for gay couples over 18 and to put the measure directly on the ballot.

Opponents argued that Democrats rushed the measure through without proper consideration of amendments once they knew there would be enough votes.

"We should not use brute force strength on such a weighty issue," said minority leader Anthony O'Donnell, R-Calvert.

Earlier in the week, opposition lawmakers criticized proponents for dragging their feet on the measure in order to have enough time to secure votes.

Source: ABC News