Galatians 4:22 For it is written that Abraham had two sons: the one by a bondwoman, the other by a freewoman.
23 But he who was of the bondwoman was born according to the flesh, and he of the freewoman through promise,
These two sons by Abraham are vastly different. The mothers concieved both of them vastly different. The attempt to thwart Gods plan and help God out, by Hagar, only results in carnal, fleshly, natural results at best. Birth is amazing, however there was nothing spectaular or out of the norm in Hagars conception. However, God had given a barren Sarah promise that she would conceive a son. Now that is a promise that only He could bring to pass. Sarah is symbolic to grace & promise where Hagar is symbolic to the law. LORD, please give your children strength to alliw You to deliver on the promises only You can give.