Three short lines, and almost nothing happens: sunlight falls on a garden through haze. Yet the poem treats it as something close to sacred. The word "holy" stands alone at the start, so it arrives before we know what it describes, and then the next line qualifies it. The light is holy "only to the haze," which suggests the sacredness isn't a grand, public truth. It belongs to a small, soft, blurred moment that only the haze, or perhaps only the person watching, can fully share.
The title, "Visitant," points to a presence that comes briefly and then goes, like a guest or a spirit. Judging by that word, the sun itself may be the visitor, drifting into the garden unannounced. The speaker seems quietly attentive and a little awed, but not showy about it. The mood is hushed, still, and gentle, with a sense that holiness can turn up in ordinary light if you happen to be looking. The sparse wording makes you slow down, much as the speaker must have done.