What will happen if one is idle according to the speaker in Ploughman by Khalil Gibran?

According to the speaker, one cannot be aligned (or enjoy closeness) with God if one is idle.

For to be idle is to become a stranger unto the seasons, and to step out of life's procession, that marches in majesty and proud submission towards the infinite.

In the poem, the speaker maintains that we truly love life when we learn how to labor. By extension, loving life through labor is the only way to be "intimate with life's inmost secret."
The speaker highlights the importance of the secret that all must discover in order to enjoy life's greatest fulfillment.

And I say that life is indeed darkness save when there is urge, And all urge is blind save when there is knowledge, And all knowledge is vain save when there is work, And all work is empty save when there is love; And when you work with love you bind yourself to yourself, and to one another, and to God.

From the above, the speaker asserts that one must not labor with an indifferent spirit or worse, with distaste. He argues that being joyful in one's work is the surest way to draw close to God; it is the secret to fulfillment. It is also the way to stay in harmony with our fellow human beings. Essentially, our joy in our work produces the greatest benefit to mankind.

For if you bake bread with indifference, you bake a bitter bread that feeds but half man's hunger. And if you grudge the crushing of the grapes, your grudge distils a poison in the wine.