si facerit te securem

from Bouvier's Law Dictionary, Revised 6th Ed (1856)
SI FACERIT TE SECUREM. If he make you secure. These words occur in the form 
of writs, which originally requited, or still require, that the plaintiff 
should give security to the sheriff that he will prosecute his claim, before 
the sheriff can be required to execute such writ. 
    

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