Neuter of a presumed derivative of martus; something evidential, i.e. (genitive case) evidence given or (specially), the Decalogue (in the sacred Tabernacle) -- to be testified, testimony, witness.
KJV: And Jesus saith unto him, See thou tell no man; but go thy way, shew thyself to the priest, and offer the gift that Moses commanded, for a testimony unto them.
NASB: And Jesus said to him, "See that you tell no one; but go, show yourself to the priest and present the offering that Moses commanded, as a testimony to them."
KJV: And saith unto him, See thou say nothing to any man: but go thy way, shew thyself to the priest, and offer for thy cleansing those things which Moses commanded, for a testimony unto them.
NASB: and He said to him, "See that you say nothing to anyone; but go, show yourself to the priest and offer for your cleansing what Moses commanded, as a testimony to them."
KJV: And whosoever shall not receive you, nor hear you, when ye depart thence, shake off the dust under your feet for a testimony against them. Verily I say unto you, It shall be more tolerable for Sodom and Gomorrha in the day of judgment, than for that city.
NASB: "Any place that does not receive you or listen to you, as you go out from there, shake the dust off the soles of your feet for a testimony against them."