Heb 8:13
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Hebrews 8:13 is explicit: “In saying ‘a new covenant,’ He has made the first obsolete”—πεπαλαίωκεν is perfect, and ἐν τῷ λέγειν anchors that action to the moment YHWH spoke through Jeremiah. The Mosaic covenant was therefore rendered obsolete by the declaration of the new one; its later disappearance was the consequence of that already-established status.

The same temporal discipline applies to Matthew 24:36: “no one knows” (οἶδεν) describes the state of knowledge when Jesus spoke those words. It does not grammatically mean, “the Son can never know.” You cannot take a statement anchored to its speaking moment and turn it into an eternal metaphysical condition.

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Hebrews 9:8 completes the thought of Hebrews 8:13. The first covenant was declared obsolete when YHWH announced the new covenant through Jeremiah, but it continued to function through the first-tabernacle arrangement until Christ fulfilled the High Priest role.

Hebrews 9 says the way into the heavenly holy places was not yet opened while that first arrangement was still standing/functioning. Then Christ entered the true heavenly sanctuary with the value of His own blood, accomplishing what the earthly priesthood only foreshadowed.

So the sequence is:

Jeremiah: the old covenant is pronounced obsolete.

Last Supper: the new covenant is instituted in Christ’s blood.

Christ’s heavenly High-Priestly entrance: the old tabernacle arrangement loses its covenant function and vanishes in fulfillment.

The priests could continue physically performing Mosaic rites afterward, but covenantally those works no longer functioned as the way to God. Christ had become the actual way into the heavenly holy places, the moment the old covenant vanished.