When the Pharisees demand a sign from Jesus, He responds with a deep sigh and a solemn refusal. In this expository message from Mark 8:10-13, Leon Pretorius traces the legitimate purpose of signs throughout Scripture — to authenticate God's messengers — and exposes the hardness of heart that lies behind demanding signs from God. Grounded in passages from Hebrews, John, Acts, and the Psalms, this sermon calls believers to humble trust in the signs God has already given, rather than testing Him for more.