Albert Barnes Commentary Psalms 121:8

"Jehovah will keep thy going out and thy coming in From this time forth and for evermore." — Psalms 121:8 (ASV)

The Lord shall preserve thou going out and thy coming in – He will preserve you in your going out and your coming in; in going from your dwelling and returning to it; in going from home and coming back; that is, everywhere and at all times. Compare (Deuteronomy 28:6). See also the notes at (Job 5:24). From this time forth, and even forevermore. Through this life and forever. This is the gracious assurance given to all who put their trust in God.

At home and abroad; in the house, in the field, and by the way; on the land and on the ocean; in their native country and in remote climes; on earth, in the grave, and in the eternal world, they are always safe.

No evil that will endanger their salvation can befall them; nothing can happen to them here except what God will see to be conducive to their ultimate good. And in the heavenly world, they will be safe forever from every kind of evil, for in that world there will be no sin, and consequently no need of discipline to prepare them for the future.

“In foreign realms, and lands remote,
Supported by your care,
Through burning climes they pass unhurt,
And breathe in tainted air.
When by the dreadful tempest borne,
High on the broken wave,
They know you are not slow to hear,
Nor impotent to save.
The storm is laid—the winds retire,
Obedient to your will;
The sea that roars at your command,
At your command is still.
In the midst of dangers, fears, and death,
Your goodness we’ll adore;
We’ll praise you for your mercies past,
And humbly hope for more.
Our life, while you preserve that life,
Your sacrifice shall be;
And death, when death shall be our lot,
Shall join our souls to you.”

Addison’s Spec.