Much can be said of the fact that Abraham surely placed the sign upon Ishmael. The question to be considered is was Ishmael in the internal aspect of the covenant or in the external aspect?
When we look at ch 21 of Genesis we see some interesting language: For example, Ishmael mocks his brother as he is weaned. God tells Abraham to toss out the bondswoman and her son as the covenant line will proceed out of Isaacs line and not the older brother. God meets with Hagar and Ishmael on the brink of death-they are out of water and have sought refuge from the elements under trees and bushes. Both the cries of mother and son via prayer are not hindered and God hears and answers in some what of an affirmative; nations will come from Ishmael’s loins. These tow were reared in a covenantal family. They knew of the means of grace and partook of them often. We know that in the book of John, it is said that God does not hear the prayers of sinners. In the absolute, we are well aware of God’s omniscience and that He hears everything. In the divided sense however, God is only inclined to the cries of His people and not of the unregenerate. This poses an interesting problem when we look at the passage in Galatians and how Paul compares those of the bondswoman and those of Isaac, i.e. the flesh vs the spirit.
Galatians 4:29 “But, as he who was born according to the flesh then persecuted him who was born according to the Spirit, even so it is now.”
It would seem conclusive that Ishmael and Hagar were of the external side of the Covenant of Grace.
Here is an interesting statement from John Lightfoot cited by Poole in Poole’s Synopsis at Gen. 25.17 which is of interest:
Gen 21:9. Signifying either by words or gestures his contempt of Isaac, and his derision of all that magnificence then showed towards his younger brother. And this carriage proceeding from a most envious and malicious disposition, and being a sufficient indication of further mischief intended to him, if ever he should have opportunity, it is no wonder it is called persecution, Gal 4:29, although the Hebrew word may be rendered beating him, as it is used 2 Sam 2:14.
And yet more on the phrase, ‘gathered to his people’:
[To his people] They vary: 1. Unto the just in limbo. [Thus some of the pontifical men.] 2. He crossed over from the state of the living to the state of the dead (Oleaster, Bonfrerius, Lapide): that is to say, he died, just as also his ancestors (Fagius). But this cannot be understood of the body (Menochius, Piscator): 1. because next mention is distinctly made of the burial of the body (Piscator): 2. from the matter itself, since his body was not with the rest of the pious (neither in his fatherland [Menochius]), but in the land of Canaan, where only the body of Sarah was laid up (Piscator). Therefore, it is to be understood of the soul, which survives after dead and immortal (Menochius, Lapide). By fathers understand the perfected spirits of the just, Hebrews 12:23. See what things are written on verse 17 (Ainsworth); Acts 13:36 (Piscator). He departed unto the heaven of the Patriarchs, etc. (Osiander4).
he was gathered to his people; to his godly progenitors, the former patriarchs, the congregation of the just in heaven, Heb 12:23; in regard of his soul: for it cannot be meant of his body, which was not joined with them in the place of burial, as the phrase is, Isa 14:20, but buried in a strange land, where only Sarah’s body lay. And it is observed, that this phrase is used of none but good men, of which the Jews were so fully persuaded, that from this very expression used concerning Ishmael here below, Gen 25:17, they infer his repentance and salvation. See this phrase, Gen 15:15; Gen 49:29; Num 20:24; Num 27:13; Judg 2:10.
In verse 17 and 20 of chapter 21, it says that ‘God heard the voice of the lad’ and ‘God was with the lad’. In verse 19 it says that God opened the eyes of Hagar. These are conflicting statements when compared to similar instances in scripture; they often resemble points of regeneration or responses of God towards His elect.
Food for thought. I don’t have a dogmatic conclusion here, but just saying….