President George W. Bush cautioned against criticizing gay couples, saying in an interview on "This Week" that you shouldn't criticize others "until you've examined your own heart."

Bush had waded into the revitalized same-sex marriage debate last week - if only barely - in a comment to a reporter in Zambia, who asked whether gay marriage conflicts with Christian values.

"I shouldn't be taking a speck out of someone else's eye when I have a log in my own," Bush said last week.

In an interview in Tanzania with ABC News Chief White House Correspondent Jonathan Karl, the former president explained his comment further.

"I meant it's very important for people not to be overly critical of someone else until you've examined your own heart," Bush told Karl.

As president, Bush opposed gay marriage, and Republicans pushed ballot measures to ban it at the state level. The topic has seen rejuvenated discussion after the Supreme Court overturned the federal ban on same-sex marriage, the Defense of Marriage Act (DOMA).

On another hot political topic - immigration - Bush said he thinks a major reform bill "has a chance to pass." In 2007, Bush sought to pass an immigration bill similar to what's been proposed in Congress this year, seeking to provide citizenship opportunity for undocumented immigrants already living in the U.S.

"It's a very difficult bill to pass because there's a lot of moving parts," Bush said on "This Week." "But it looks like they're making some progress."

Bush said immigration is important to pass because of a "broken system," not to improve the Republican Party's political standing among Latino voters.

"Good policy yields good politics, as far as I'm concerned," Bush said.

Read more on former President George W. Bush's comments on Egypt here

The 43rd president traveled to Africa with former first lady Laura Bush to promote their Pink Ribbon Red Ribbon initiative, a program through their foundation to expand care and prevention of cervical cancer in sub-Saharan Africa and Latin America. Last week, the Bushes helped renovate a clinic in Zambia that will serve as a cervical-cancer screening and treatment center.

As president, Bush launched the President's Emergency Plan for AIDS Relief (PEPFAR), to address the wide spread of HIV/AIDS in Africa. Since leaving the White House, he has received warm welcomes on the continent.

"People admire America," Bush told Karl on "This Week." "Africans are thrilled with the idea that American taxpayers funded programs that save lives."

To anyone who says his work in Africa is an attempt to make up for mistakes made elsewhere during his presidency, Bush called that notion "absurd psychobabble."