Be near me when my light is low, When the blood creeps, and the nerves prick And tingle; and the heart is sick, And all the wheels of Being slow.
Be near me when the sensuous frame Is rack'd with pangs that conquer trust; And Time, a maniac scattering dust, And Life, a Fury slinging flame.
Be near me when my faith is dry, And men the flies of latter spring, That lay their eggs, and sting and sing And weave their petty cells and die.
Be near me when I fade away, To point the term of human strife, And on the low dark verge of life The twilight of eternal day.
Tennyson's getting all commanding in this canto, so it seems to signal a shift from doubts and the way he's been juggling ideas of rebirth and resurrection to...something else. We don't quite have enough info yet.
Each stanza here starts with "Be near me" (that's more anaphora for you). We're going to drop some more grammar on you. This form of the verb is called the imperative, which means the command form. In other words, the speaker is ordering the spirit of Arthur around.
First, he commands Arthur's spirit to be with him when he's slow and sluggish and not feeling very well.
Next, he orders him to be around when he's being tortured ("rack'd") with doubt. When this happens, time seems to move quickly, and life feels like someone taking revenge out on him. (Don't know what a Fury is? Better check "Allusions"stat.)
He's appealing to Arthur to be with him as he contemplates the utter meaninglessness of life. He's going full emo in the third stanza. He compares men to flies laying eggs (um...eww) and suggests by this image that their actions are just as petty as when the flies go about their business and soon die.
Finally, he demands that Arthur be with him as he dies, so that he can guide him from his earthly existence to whatever immortal realms might lie beyond.