Exodus 6:9
And Moses spake so unto the children of Israel: but they hearkened not unto Moses for anguish of spirit, and for cruel bondage. And Moses spake so unto the children of Israel: but they hearkened not unto Moses for anguish of spirit, and for cruel bondage.
Moses told Israel that God would free them from Egyptian burdens, redeem them with great judgments, take them as His people, and give them the land promised to Abraham, Isaac, and Jacob. They did not listen to this renewed promise of deliverance because anguish and cruel bondage had crushed their spirits, leaving them unable to take in his message.
Their refusal left Moses discouraged and led him to argue that if God's own circumcised people would not listen to him, Pharaoh as an uncircumcised idolater would certainly not listen to him.