"If you're openly living in unrepentant sin, whatever it may be, not just homosexuality, adultery, fornication, premarital sex between heterosexuals, whatever it may be. I think that's walking in open rebellion to God and to Jesus Christ," he said.
NFL receiver Mike Wallace tweeted Monday: "All these beautiful women in the world and guys wanna mess with other guys SMH."
He tweeted again, saying he was being misinterpreted.
"Never said anything was right or wrong I just said I don't understand!! Deeply sorry for anyone that I offended," he wrote.
The Dolphins, Wallace's employer, issued a statement saying the team has spoken with Wallace about the tweets. The team said it will address its policy of inclusion with all of its players.
NBA Commissioner David Stern said Collins, a 34-year-old veteran, is widely respected in the league.
"We are proud he has assumed the leadership mantle on this very important issue," he said in a statement.
Washington Wizards President Ernie Grunfeld said the team is "extremely proud of Jason and support his decision to live his life proudly and openly."
"He has been a leader on and off the court and an outstanding teammate throughout his NBA career. Those qualities will continue to serve him both as a player and as a positive role model for others of all sexual orientations," Grunfeld said.
Boston Celtics head coach Doc Rivers called Collins "a pro's pro" and one of his favorite players he ever coached.
"If you have learned anything from Jackie Robinson, it is that teammates are always the first to accept," Rivers said. "It will be society who has to learn tolerance."
Bill Clinton called the announcement an "important moment for professional sports and in the history of the LGBT community."
Collins, who had been traded by the Celtics to the Wizards this season, wrote in his essay that U.S. Rep. Joe Kennedy, D-Massachusetts, helped prompt his decision to come out as gay. Kennedy and Collins were roommates at Stanford. He recounts hearing about Kennedy, who is not gay, marching in Boston's Gay Pride Parade.
"For as long as I've known Jason Collins he has been defined by three things: his passion for the sport he loves, his unwavering integrity, and the biggest heart you will ever find," Kennedy said. "I'm proud to stand with him today and proud to call him a friend."
President Barack Obama called Collins "to express his support and said he was impressed by his courage," a White House official said.
Active players posted their approval on Twitter. The Los Angeles Lakers' Kobe Bryant said: "Proud of @jasoncollins34. Don't suffocate who u r because of the ignorance of others." Steve Nash, also a Laker, said: "The time has come. Maximum respect."
Two Wizards players, Garrett Temple and Bradley Beal, said in tweets they were "proud" of Collins. "Much respect to my teammate," Temple said. "Great teammate, mentor and better person," said Beal.
Collins' announcement comes after the end of the Wizards' season, and he is no longer under contract. He is an "old" player by NBA standards who has never been a star. So will he play in the NBA this fall?
ESPN.com said only six of 14 team officials reached for an unofficial poll Monday thought he would be back in the league. If he does return, he probably will play only a few minutes a game for a team that needs a veteran leader, the other executives told ESPN.com.
Some male athletes have come out as gay after they've left professional sports. One is John Amaechi, a former NBA player.
Amaechi told CNN he hopes Collins will be a catalyst for a wider acceptance of openly gay athletes, saying he believes Collins is better equipped than anyone who came before him to handle the attention that will come his way. But it may take more, Amaechi said.
People like to believe one iconic figure can change things, he said, "but the reality is that when there's this tipping point, or enough people coming together deciding that change is necessary, that's when change happens."
The Women's National Basketball Association, the women's pro league, has had its share of milestones and openness as far as gays are concerned. In 2005, Sheryl Swoopes, a top player in the WNBA, announced she was gay.
Brittney Griner, the No. 1 pick in this year's WNBA draft, recently said in an interview with Sports Illustrated that she is gay. Griner finished her college career as the NCAA's all-time leading shot-blocker with 748 and as the No. 2 all-time scorer with 3,283 points.