In a Wall Street Journal op-ed, he writes:

During the negotiations over raising the debt ceiling, President Obama reportedly warned Republican leaders not to call his bluff by sending him a bill without tax increases. Republicans in Congress ignored this threat and passed a bill that cuts more than a dollar in spending for every dollar it increases the debt limit, without raising taxes.
Yesterday, Mr. Obama signed this bill into law. He was, as he said, bluffing.

In fact, every media outlet has reported that Obama said this not with regard to passing a debt ceiling hike without tax increases, but in response to a Republican proposal to pass a short-term debt ceiling extension. This is not a subject of partisan dispute. Even Eric Cantor's version of the exchange confirms this:

The Cantor version:
Immediately upon leaving the White House on Wednesday night, Mr. Cantor and his aides offered their description of the clash.
It came at the end of the meeting, they said, when Mr. Cantor complained that Mr. Obama was constantly changing the amount of spending he was willing to cut, and Mr. Cantor raised the idea of increasing the debt limit in small, temporary increments over the next 18 months.
What about a short-term goal, Mr. Cantor asked?
The president “got very agitated, seemingly,” Mr. Cantor told reporters.
“Eric, don’t call my bluff,” the president said, according to Republican aides. “I’m going to the American people with this.”

I suppose what's interesting here is that Ryan is trying to present Obama as a weakling rather than as a fearsome, tax-crazed socialist.