Verse 1-2
Psalms 121:1-2. I will lift up mine eyes unto the hills — To Zion and Moriah, called the holy mountains, Psalms 87:1, the hills on which the tabernacle or temple stood, where were the ark of the covenant, the oracle, and the altars. I will have an eye to the special presence of God in his church, and with his people, and from thence I will expect help. My help cometh from the Lord — From God alone, and therefore to him alone will I turn mine eyes; which made heaven and earth — And therefore how great soever my straits and difficulties may be, he has power sufficient for my succour and relief.

Verses 3-8
Psalms 121:3-8. He will not suffer thy foot to be moved — To wit, so as to fall into mischief. He speaks, as it were, from God to himself, but, withal, to the encouragement of all good men. He that keepeth thee will not slumber — Will not overlook nor neglect any thing which is necessary for thy preservation. The Lord is thy shade upon thy right hand — Both to refresh thee, and keep thee from the burning heat of the sun. In those countries where the heat of the sun was intolerable, shady places were esteemed not only very refreshing, but likewise salutary, and necessary to the preservation of health and life. When, therefore, the psalmist styles God his shade, he means that he protected him from danger, and refreshed him with comforts. The sun shall not smite thee by day — With excessive heat; nor the moon by night — With that cold and damp which come into the air by it. Intemperate heats and colds are the springs of many diseases. And, “as the heat of the sun by day, so the copious dews, which fall most abundantly in the moonshine, were very pernicious in those countries.” The sense is, He shall protect thee from all evils, both day and night. The Lord shall preserve thy going out and coming in — Shall guard and assist thee in all thy expeditions, journeys, and affairs, both at home and abroad; from this time forth, and even for evermore — He will be thy guide even unto death, and then bring thee to his heavenly kingdom. God will protect his church and his saints always, even to the end of the world; the Spirit, which is their preserver and comforter, shall abide with them for ever.