The question the disciples ask, even though it appears to be rhetorical, is an appropriate one for Christians as well, especially so during the Lord’s supper. It was during the Passover/establishment of the supper that they asked it, when Jesus said that one of them would betray him.
They were distressed, and one by one said to him, “Surely not I?”
Mark 14.19 NET
Would I betray him? Would I deny him? Would I abandon him when the enemies come?
Let us beware of answering too quickly, too flippantly.
The passage led Matthew Henry to pray:
Lord, give me grace to keep me from denying thee.
Hold this thought: Weak am I when under duress, / I need God’s strength, in faith, to confess.