White garments and perfume are simply an expressive sign of joy.

Let thy garments be always white - The Jews wore white garments on festal occasions, as emblems of joy and innocence. Be always pure, and always happy. The inhabitants of India are all dressed in clean white cotton, and to this is the allusion in the text.
The Targum says: "At all times let thy garments be washed and pure from the stain of sin. Acquire a good name, which is likened to the oil of anointing, that blessings may be called down up thy head, and goodness not forsake thee."

Let thy garments be always (e) white; and let thy head lack no ointment.
(e) Rejoice, be merry and spare for no cost, thus speak the wicked belly-gods.

Let thy garments be always white,.... That is, neat and clean, not vile and sordid; what is comely and decent, and suitable to a man's circumstances; this colour is particularly mentioned because much used in the eastern countries, and in Judea; hence we so often read of washing garments, and of fullers that whitened them; and especially on festival days and days of rejoicing, to which Horace (a) refers; and here it signifies that every day should be like a festival or day of rejoicing to a good man, to whom God has given the garment of praise for the spirit of heaviness, Isaiah 61:3; and though there may be times for mourning, and so of putting on other apparel, yet, in common and ordinarily, this should be the habit, decent and comely apparel. The ancient Jews in Aben Ezra, and so Jarchi, interpret it of an unblemished conversation; and Kimchi (b) of repentance and good works; and so the Targum,
"let thy garments be white (or washed) from all filth of sin;''
or be without any spot of sin, as Alshech; the conversation garments of the saints are made white in the blood of Christ, and his righteousness is fine linen, and white; and even eternal glory and happiness is signified by walking with him in white, Revelation 7:14;
and let thy head lack no ointment: which used to be poured plentifully on the heads of guests at feasts (c), for the refreshment of them, which gave pleasure, and a sweet odour and fragrancy, and was much in use in those hot countries; see Psalm 23:5; and is opposed to a gloomy and melancholy carriage and deportment, Matthew 6:17; hence we read of the oil of joy and gladness, Psalm 45:7. The Jews before mentioned interpreted this of a good name better than ointment, Ecclesiastes 7:1. So the Targum,
"and a good name, which is like to anointing oil, get; that blessings may come upon thy head, and thy goodness fail not.''
(a) "Ille repotia natales aliosque dierum, festos albatus celebret". Satyr. l. 2. Sat. 2. v. 60, 61. "Cum ipse epuli Dominus albatus esset", Cicero in Vatin. c. 13. (b) Comment. in lsa. lxv. 13. (c) "Coronatus nitentes malabathro Syrio capillos", Horat. Carmin. l. 2. Ode 7. v. 7, 8. "et paulo post: funde capacibus unguenta de conchis", v. 22, 23. "Unguentum (fateor) bonum dedisti convivis", Martial. l. 3. Epigr. 11.

white--in token of joy (Isaiah 61:3). Solomon was clad in white (JOSEPHUS, Antiquities, 8:7,3); hence his attire is compared to the "lilies" (Matthew 6:29), typical of the spotless righteousness of Jesus Christ, which the redeemed shall wear (Revelation 3:18; Revelation 7:14).
ointment-- (Psalm 23:5), opposed to a gloomy exterior (2-Samuel 14:2; Psalm 45:7; Matthew 6:17); typical, also (Ecclesiastes 7:1; Song 1:3).

The white garments, לבּנים, are in contrast to the black robes of mourning, and thus are an expression of festal joy, of a happy mood; black and white are, according to the ancients, colour-symbols, the colours respectively of sorrow and joy, to which light and darkness correspond.
(Note: Cf. Shabbath 114a: "Bury me neither in white nor in black garments: not in white, because perhaps I may not be one of the blessed, and am like a bridegroom among mourners; not in black, because perhaps I may be one of the blessed, and am like a mourner among bridegrooms." Semachoth ii. 10: Him who is outside the congregation, they do not bury with solemnity; the brothers and relatives of such must clothe and veil themselves in white; cf. Joma 39b. Elsewhere white is the colour of innocence, Shabbath 153a, Midrash under Proverbs 16:11; and black the colour of guilt, Kiddushin 40a, etc.)
Fragrant oil is also, according to Proverbs 27:9, one of the heart-refreshing things. Sorrow and anointing exclude one another, 2-Samuel 14:2; joy and oil stand in closest mutual relation, Psalm 45:8; Isaiah 61:3; oil which smooths the hair and makes the face shine (vid., under Psalm 104:15). This oil ought not to be wanting to the head, and thus the perpetuity of a happy life should suffer no interruption.

White - The eastern people of the best sort, used white garments, especially in times of rejoicing. Ointment - Which upon joyful occasions was poured upon mens heads.