The Greek adjective blēteos (G992) is a verbal adjective (gerundive) derived from ballō (to throw/put) meaning "must be put" or "must be cast." It expresses necessity — what ought or must be done. It appears in Luke 5:38 (and Matthew 9:17 variant) in the parable of new wine and new wineskins.
The use of blēteos — "must be put" — in Jesus's parable of the wineskins carries the force of divine necessity. New wine of the Kingdom cannot be contained in old structures. The new covenant that Jesus brings requires new vessels — transformed hearts and minds rather than rigid religious forms. This teaching is foundational to understanding the discontinuity between the old covenant administration and the new.