I am a stranger on the earth. It is proper to inquire into the reason for his calling himself a sojourner and stranger in the world. The great concern of the unholy and worldly is to spend their life here easily and quietly; but those who know that they have their journey to pursue, and have their inheritance reserved for them in heaven, are not engrossed nor entangled with these perishable things, but aspire after that place to which they are invited. The meaning may be thus summed up: "Lord, since I must pass quickly through the earth, what will become of me if I am deprived of the doctrine of thy law?" We learn from these words from what point we must commence our journey, if we would go on our way cheerfully unto God. Besides, God is said to conceal his commandments from those whose eyes he does not open, because, not being endued with spiritual vision, in seeing they see not, so that what is before their eyes is hid from them. And, to demonstrate that he does not present his request in a careless manner, the prophet adds, that his affection for the law is most intense; for it is no common ardor which is expressed by him in the following language, My soul is rent with the desire it hath at all times unto thy judgments. As the man who may concentrate all his thoughts on one point with such intensity as almost to deprive him of the power of perception, may be said to be the victim of his intemperate zeal, so the prophet declares the energy of his mind to be paralyzed and exhausted by his ardent love for the law. [1] The clause, at all times, is meant to express his perseverance; for it may occasionally happen that a man may apply himself with great ardor to the study of the heavenly doctrine; but it is only temporary-his zeal soon vanishes away. Steadfastness is therefore necessary, lest, through weariness, we become faint in our minds.

Footnotes

1 - "Every intense exertion of mind has an influence, if it be long continued, to exhaust and impair the faculties in some degree. Such an effect is here alluded to; the close and assiduous attention which the Psalmist had paid, and the exertion of strong desire which he had exercised, produced the feeling which he here speaks of. He is also to be regarded as using the language of poetry, which admits of stronger colouring than prosaic description." -- Walford.

I am a stranger in the earth - A wayfaring man; a pilgrim; a so-journer; a man whose permanent home is not in this world. The word is applicable to one who belongs to another country, and who is now merely passing through a foreign land, or sojourning there for a time. Compare the notes at Hebrews 11:13. The home of the child of God is heaven. Here he is in a strange - a foreign - land. He is to abide here but for a little time, and then to pass on to his eternal habitation.
Hide not thy commandments from me - Make me to know them; keep them continually before me. In this strange land, away from my home, let me have the comfort of feeling that thy commands are ever with me to guide me; thy promises to comfort me. The feeling is that of one in a strange land who would desire, if possible, to keep up constant communications with his home - his family, his friends, his kindred there. On earth, the place of our sojourning - of our pilgrimage - the friend of God desires to have constant contact with heaven, his final home; not to be left to the desolate feeling that he is cut off from all contact with that world where he is forever to dwell.

I am a stranger in the earth - In the land. Being obliged to wander about from place to place, I am like a stranger even in my own country. If it refer to the captives in Babylon, it may mean that they felt themselves there as in a state of exile; for, although they had been seventy years in it, they still felt it as a strange land, because they considered Palestine their home.

I [am] a (b) stranger in the earth: hide not thy commandments from me.
(b) Seeing man's life in this world is only a passage, what should become of him, if your word were not his guide?

I am a stranger in the earth,.... As all his fathers were, and all the saints are; not to divine and spiritual things; to God, and communion with him; to Christ, and the knowledge of him; to the Spirit, and his operations in their hearts; to their own hearts, and the plague of them; to the Gospel, and its truths; nor to the people of God, and fellowship with them: but to the world, among whom they are, not being known, valued, and respected by them; and they also behaving as strangers to the world, having no fellowship with them in their sinful works; as also not being natives here, but belonging to another city and country, an heavenly one; see 1-Chronicles 29:15;
hide not thy commandments from me; the doctrines of the Gospel, the word which God has commanded to a thousand generations; which is pure, and enlightens the eyes, and so needful to strangers in their pilgrimage, Psalm 19:8; which God sometimes hides from the wise and prudent, and which the psalmist here deprecates with respect to himself, Matthew 11:25. Or the precepts of the world may be meant, which are a light to the feet, and a lamp to the paths, a good direction to travellers and strangers in the way: David, being such an one, prayed that these might not be hid from him, but be showed unto him; that he might know his way, and not go out of it; but walk as a child of light, wisely and circumspectly.

A stranger - I am not here as in my home, but as a pilgrim travelling homeward in a strange land. Commandments - Which are my chief support and guide in my pilgrimage.