διαθήκης, (diathekes) in Matthew 26:28: Noun Genitive Singular Feminine

Noun: the form names a person, place, thing, quality, or concept in the clause.

Genitive: the noun defines the covenant relation of the blood phrase.

Singular: the form presents covenant as a singular covenant reality in this saying.

Feminine: the feminine form marks grammatical class and agrees with καινῆς.

τῆς καινῆς

The noun stands in a genitive relation after the blood statement.

It identifies Jesus' blood in covenant terms.

It does not by itself explain every covenant theme across Scripture or every later theological formulation.

High: The noun frames Jesus' blood in covenant terms.

Genitive covenant descriptor. identifies the blood as covenantal. Attached to τὸ αἷμά μου. Governed by Jesus' cup saying. The noun should be read with new and with the poured-out-for-forgiveness clause.

What covenant relation does Jesus name? He speaks of his blood of the new covenant.

Direct: The form directly supports the rendering "covenant."

The genitive relation is clear, but broader covenant theology requires broader biblical context.

Covenant noun alone settles every covenant question: This occurrence identifies Jesus' blood covenantally; broader covenant doctrine needs the whole canon.

The witness reads διαθήκης, in Matthew 26:28.

The lemma διαθήκη means covenant, will, or testament, and here the genitive identifies the covenant relation of Jesus' blood.

The genitive noun is modified by καινῆς and attaches to the blood saying as a covenant descriptor.

Jesus speaks of his blood as the blood of the new covenant.

The form connects Jesus' death to covenant fulfillment and the forgiveness language in the same verse.

In teaching, explain the genitive relation without turning the form into a full covenant theology on its own.

Do not make the genitive noun alone settle every continuity and discontinuity question about covenant.