Radak: They thought that they enticed Him, but He is not enticed, for He knows their hearts. Even so, His Midah of mercy atones for those who appear to repent, but He does not totally atone for them, just like they do not repent with a full heart. Rather, He punishes for their sin and does not totally destroy, and diverts His anger from them. He does not arouse all His anger against them, only part. Because their Teshuvah is not full, their pardon is not full.

Malbim: They said so only with their mouths, because He killed them. The words connote matters of understanding. Via their investigation in this, they spoke Sheker, and made philosophical investigations to deny Hashem.