The passage you may be referring to is: Exodus 32:32: "Yet now, if You will forgive their sin - but if not, I pray, blot me out of Your book which You have written."
Ekesedo 32:32 Le fa go ntse jalo, fa jaana o ka ba itshwarela boleo; mme fa go sa nna jalo, a ko o mphimole mo lokwalong lwa gago lo o lo kwadileng."