Romans 9:11, 16

and though the twins were not yet born and had not done anything either good or bad, so that God’s purpose [His choice, His election] would stand, not because of works [done by either child], but because of [the plan of] Him who calls them

So then God’s choice is not dependent on human will, nor on human effort [the totality of human striving], but on God who shows mercy [to whomever He chooses—it is His sovereign gift].