Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
per-sisto, stĭti, 3, v. n., to continue steadfastly, to persist (rare): si perstiteris ad corpus ea referre, Cic. Fin. 2, 33, 107 fin.: in impudentiā, Liv. 38, 14, 11: in luxuriā, Treb. Poll. Gall. 4, 2: in oratione persistens cum lacrymis, Vulg. Tob. 3, 11: divulsusque triens prohibet persistere bessem, to remain, permanere, Aus. Ecl. 1, 22.