The passage as a whole makes the sense (even with the old English spellings) as a specific admonition against teaching overzealously in the original 1582 DR translation. Teaching overzealously will allow the devil into your heart and lead to perversities, I believe that it allegorically also applies to what z_0101states above as well.
“Can, my brethren, the figge tree yeld grapes or the vine, figges? So neither can the salt water yeld sweete. Who is wise and hath knowledge among you? Let him shew by good conversation his working in mildeness of wisdom. But if you have bitter zeale, and there be contentions in your hartes: glorie not and be not liers against the truth, for this is not wisdom descending from above: but earthly, sensual, divelish. For where zeale and contention is: there is inconstancie, and every perverse work. But the wisdom that is from above, first certes is chast: then peacable, modest, susasible, consenting to the good, ful of mercie and good fruites, not judging, without limulation. And the fruite of justice, in peace is sowed, to them that make peace.” (spelling as in the original).