In this week's parsha we find that Hashem tests Avraham's loyalty by telling him to sacrifice his son, Yitzchak. Why after waiting so long for Sarah to give birth to a child, and along with her cry to Hashem to have a child, must Avraham sacrifice Yitzchak? Two great actions are performed by Avraham. First, Avraham accepts Hashem's command. Second, Avraham travels through many obstacles that Hashem puts in his path whether to see if Avraham will give up or continue onward in an attempt to fulfill Hashem's command. Chazal explain the reasons why Hashem issued this command are that Hashem wanted Avraham to reach a higher spiritual level of his belief of Hashem, and Hashem wanted Avraham to demonstrate to the entire world his belief in Hashem (see Breishit Rabbah).