The fairy land buys not the child of me.
His mother was a vot’ress of my order:
And, in the spiced Indian air, by night,
Full often hath she gossip'd by my side,…
But she, being mortal, of that boy did die;
And for her sake do I rear up her boy,
And for her sake I will not part with him.
According to the following lines, why does Titania not want to give up the boy to Oberon?