After years of disappointment, Sarah received the promised son. After bringing up Isaac as an offering, Abraham received him back and opened the way for the promised seed to come in the person of Yeshua, who is our hope.
God tested Abraham for his own benefit. By demonstrating his faith through his actions, he received greater reward and accomplished much for the Kingdom.
Through Yeshua we are brought into the kingdom of priests. Having our hands cleansed and our hearts purified, we may draw near to God, being changed from glory to glory back into beings of light, as it was in the beginning.