“What is the promise the writer is talking about in Hebrews 11:39?”
“And these all, having obtained a good report through faith, received not the promise.”
God “promised” the Old Testament saints mentioned here a Savior (Jer. 33:14,15; Acts 13:23) that they didn’t live to receive (Luke 10:24). He also “promised” them eternal life in the kingdom of heaven on earth (James 2:5), a kingdom in which He “promised” to save them from their enemies (Luke 1:71,72), which amounted to a “promise” of rest (Heb. 4:1). He also “promised” the people of Israel the land of Israel (Deut. 19:8; Acts 7:5), from which He promised they would rule “the world” in the millennial kingdom (Rom. 4:13; Rev. 5:10) and then in the new earth (2 Pet. 3:13).
All those Hebrews 11 heroes of faith died “not having received the promises” (Heb. 11:13) plural. But when verse 39 says they “received not the promise” (singular), we know the specific “promise” must be that of the resurrection (cf. Acts 26:6-8), for the next verse says:
“God having provided some better thing for us, that they without us should not be made perfect” (Heb. 11:40).
The Lord was “made perfect” when He rose from the dead (Heb. 5:8,9). And while the “spirits” of those Old Testament saints have already been “made perfect” (Heb. 12:23), their bodies won’t be made perfect and reunited with their perfected spirits until the resurrection. The writer of Hebrews says that it was “better” for him and his fellow New Testament Hebrew saints that the resurrection hadn’t taken place back in Old Testament times without them.