Which preposition to use with benigna

in Occurrences 1%

But when as I say, nox, vinum, et adolescentia, youth, wine, and night, shall concur, nox amoris et quietis conscia, 'tis a wonder they be not all plunged over head and ears in love; for youth is benigna in amorem, et prona materies, a very combustible matter, naphtha itself, the fuel of love's fire, and most apt to kindle it.

Which preposition to use with  benigna