This Bible contradiction is from the EvilBible.com.
Abraham begat a son when he was a hundred years old, by the interposition of providence
Genesis 21:2 View context
For Sarah conceived, and bare Abraham a son in his old age, at the set time of which God had spoken to him.
Romans 4:19 View context
And being not weak in faith, he considered not his own body now dead, when he was about an hundred years old, neither yet the deadness of Sara's womb:
Hebrews 11:12 View context
Therefore sprang there even of one, and him as good as dead, [so many] as the stars of the sky in multitude, and as the sand which is by the sea shore innumerable.
Abraham begat six children more afterward without help
Genesis 25:1-2 View context
Then again Abraham took a wife, and her name [was] Keturah.
And she bare him Zimran, and Jokshan, and Medan, and Midian, and Ishbak, and Shuah.