Sentence:  And opportunity I here have had / To try thee, ſift thee, and confeſs have found thee / <WSD>Proof</WSD> againſt all temptation as a rock / Of Adamant, and, as a Center, firm / To the utmoſt of meer man both wiſe and good, / Not more; ... 
Meaning of the word marked with <WSD> tags:  Firm or successful in resisting.