This Bible contradiction is from the Skeptic's Annotated Bible.

Verses

Saul inquired of the Lord.

1 Samuel 28:6 View context

And when Saul enquired of the LORD, the LORD answered him not, neither by dreams, nor by Urim, nor by prophets.

Saul did not inquire of the Lord.

1 Chronicles 10:13-14 View context

So Saul died for his transgression which he committed against the LORD, [even] against the word of the LORD, which he kept not, and also for asking [counsel] of [one that had] a familiar spirit, to enquire [of it];

And enquired not of the LORD: therefore he slew him, and turned the kingdom unto David the son of Jesse.