Isaac: 3. The Son and Heir Born

Genesis 21:1-7
The set time was now come. The child of promise was at hand. Many and various had been the premonitions on the one side, and checks on the other; but at length in the face of weakness and drawbacks, of unfaithfulness with gracious overruling, the divine word is proved to be, as it is, unfailing and worthy of all trust.
“And Jehovah visited Sarah as he had said, and Jehovah did to Sarah as he had spoken. And Sarah conceived and bore Abraham a son in his old age at the appointed time of which God had spoken to him. And Abraham called the name of his son that was born to him, whom Sarah bore to him, Isaac. And Abraham circumcised his son Isaac when he was eight days old, as God had commanded him. And Abraham was a hundred years old when Isaac was born to him. And Sarah said, God hath made me laugh: everyone that heareth will laugh with me. And she said, Who would have said to Abraham, Sarah will give children suck? for I have borne a son in his old age” (vers. 1-7).
Here the usage of the divine designations comes before us remarkably. To impute the difference to distinct authors is the despairing or malevolent resource of uubelieving ignorance. First of all “Jehovah” occurs with emphatic repetition (ver. 1). Governmental relationship was in question; and as Jehovah had promised, so also did He show Himself faithful to perform. But it was of no less moment in the next place to indicate that He who thus spoke was God in the supremacy of His nature (ver. 2). Hence “Elohim” is employed, and throughout the chapter, till ver. 33 where relative dealings properly demand the name of “Jehovah Elohim,” as will be shown in due course.
But beyond controversy it was the birth of one who here typifies the Son of Psa. 2:7, 127I will declare the decree: the Lord hath said unto me, Thou art my Son; this day have I begotten thee. (Psalm 2:7)
12Kiss the Son, lest he be angry, and ye perish from the way, when his wrath is kindled but a little. Blessed are all they that put their trust in him. (Psalm 2:12)
. This explains why there should have been so many prophetic intimations to prepare the way. This accounts for the serious consequences which followed for such as despised Him when come. So the prophet was given to say, more than seven centuries before the event (Isa. 9:66For unto us a child is born, unto us a son is given: and the government shall be upon his shoulder: and his name shall be called Wonderful, Counsellor, The mighty God, The everlasting Father, The Prince of Peace. (Isaiah 9:6) and following): “For to us a child is born, to us a son is given; and the government shall be upon his shoulder. And they shall call his name Wonderful, Counselor, Mighty God, Father of eternity, Prince of peace.” The prediction, glowing and glorious as it is, has nothing to do with His being First-born from the dead, Head of the body, the church, Who is the beginning. It belongs to His other Headship, as born into the world, the Firstborn of all creation. For in all things He must have the supreme place.
Hence we can see that Calvin only expresses the prevalent confusion of these two relationships, when He says that in this chapter God has set before us a lively picture of His church.
Not so. It is not “the mystery” which is here foreshewn, but the new covenant; it is the mother,1 and not the bride. Consequently the Christian has already new covenant blessing in the death of the Savior; but the scripture which most fully explains it to us (2 Cor. 3) points to its being in spirit rather than in letter; it will be formally with both houses of Israel in the day which fast approaches, and forever. But Israel, however richly blessed in that day, will not have the union with Christ as His body, which is ours even now with Him Who is head over all things. And this involves the most important differences, as widely apart as heaven is from earth, of which this is not the place to speak more particularly. The distinction however cannot well be over-estimated.
Next in ver. 3 Abraham called his new-born son Isaac. So he was now, whatever had gone before, whatever might come after. Any laughter of doubt had given place to the joy of grace. And Abraham certainly looked on with joy to wide, deep, and enduring results; he rejoiced that he should see Christ's day, and he saw it and was glad. How blessed will it be for Israel and the earth and all the nations and every creature of God! How different from the day of Massah and Meribah in the wilderness; when man hardened his heart and Jehovah was grieved long years with a generation that erred in their heart and knew not His ways! In that day what singing aloud to Jehovah, what shouting for joy to the rock of salvation, and coming before His face with thanksgiving and psalms! Yea, the heavens shall rejoice and the earth be glad; the sea shall roar and the fullness thereof; the field shall exult and all that is therein. Then shall all the trees of the forest sing for joy before Jehovah, for He cometh-for He cometh to judge the earth: He will judge the world with righteousness, and the people in His faithfulness (Psa. 96). Isaiah bears the same witness at intervals from his first chapter to his last, notably in 11; 12; 24-27; 30; 32; 35; 40-45; 49-55; 60-62; 65. So we may say in general have all the prophets spoken. So much the more lamentable is the unbelief which merges all in the church's blessings, only to lose its heavenly bridal place to no end obscured by that groundless confusion.
But the joy of Abraham in no way weakened his duty of subjecting his son to the sign of death for the flesh. He circumcised Isaac duly when he was eight days old, “as God had commanded him” (ver. 4). The eighth day points to resurrection in contrast with nature. Circumcision was instituted, not when Ishmael was born, but in view of Isaac, the seal of the covenant. The principle was God's righteousness. Man was judged as evil and flesh mortified.
It is notified in ver. 5 that Abraham was a hundred years of age when Isaac was born. Faith had indeed to wait, but was in no way disappointed: God is faithful. “And Sarah said (ver. 6), God hath made me laugh; every one that heareth will laugh with me.” She had laughed at first when Jehovah announced the set time for her to be a mother, and she added the shame of untruth when taxed with it (chap. 18). But all is here changed by grace. God, she owns, made her laugh now. It was no longer within herself, but of Him; and others who heard would share her joy. “And she said (ver. 7), Who would have said to Abraham, Sarah will give children suck? For I have borne a son in his old age.” Sarah is thenceforth, old as she was, become a child of wisdom; and wisdom is justified of all her children.