This question is about understanding a verse in a poem by Han Yu of the Tang dynasty.
The buckwheat(?) can grow well in the snow because of its inherent ability.
A gentleman can live well in the predicaments, then people can see his inner integrity.
薺麥之茂 -> 薺麥的茂盛 -> The lushness of chestnut wheat
薺麥之有 -> (來自)薺麥的內在(飽滿)。-> (comes from) chestnut wheat's inside(plumpness)
君子之傷 -> 君子的困苦 -> a gentleman's hardship
君子之守 -> (彰顯)君子的操守 -> (emphasize) a gentleman's integrity
薺麥之茂，薺麥之有。"The lushness of chestnut wheat comes from their inner plumpness," (substance)
君子之傷，君子之守。"A gentleman shows his personal integrity during hardship."
*"Chestnut wheat has substance. Therefore, they are lush outside; a gentleman has substance. Therefore, he shows integrity during hardship."
因 = cause; reason
因有 = there's cause /reason
荠麦之因有也 = there's reason within the chestnut wheat (it has substance)