Song lyrics are often complex, because (like poetry) they try to evoke emotion with layered meanings.
First, let's look at "getting me high, and making me low". To "get high" means to reach a state of euphoria or bliss, often through the use of drugs. Conversely, to be "low" means to be depressed, dejected, or diminished. In context, it means "that blue" is creating both positive and negative emotions.
Blue is ambiguous here. It could refer to her eye color, and he could be so struck by her beauty that he is moved to these emotions. However, it's also worth noting that "blue" is also a common way to refer to sadness, so it's possible he is reacting to her emotions. He could also be referring to his own emotions in reaction to her eyes.
As I said, ambiguous.
Like many songs in the "country" or "bluegrass" genres, this is a Gospel song:
Gospel music is a genre of Christian music. The creation, performance, significance, and even the definition of gospel music varies according to culture and social context. Gospel music is composed and performed for many purposes, including aesthetic pleasure, religious or ceremonial purposes, and as an entertainment product for the marketplace. Gospel music usually has dominant vocals (often with strong use of harmony) with Christian lyrics.
The Christian theme should help us interpret the lyrics. Overall, the song is about someone who is dying and is feeling joyful about going to Heaven.
In this specific line, "God's Redeemed" are those Christians who have been saved and are already in Heaven. See more information here about what this means and why some Christians like to call themselves "redeemed".
Vigil (n): A period of keeping awake during the time usually spent asleep, especially to keep watch or pray.
This definition is, I think, too narrow. A "vigil" is a period of waiting and watching, usually for something to happen, or to guard against something happening. There are many kinds of vigils, but this case evokes the image of a group of waiting/watching "protectors" or "guiding spirits".
Grammatically the line uses a form of literary inversion to place the verb at the end of the sentence rather than its usual place in the middle. One famous example of inversion is the opening line of the epic poem Kubla Khan by Samuel Coleridge:
In Xanadu did Kubla Khan / A stately pleasure-dome decree
Inversion adds extra drama and significance to a sentence, and should only be used if you intend to sound overly dramatic (and somewhat archaic). Example:
The general rallied his men, crying, "On this ground we stand, and to no man nor god shall we yield!"
Taken as a whole, "Where Gods redeemed their vigils keep" means something like:
(In Heaven) where those who have been saved have been waiting for me.
Best Answer
First of all, note this song is a gospel song, written as a kind of dirge. So there is a religious context, and it's somewhat mournful, as if it is about death and dying.
The rest of the lyrics list various kinds of sinners -- friends who lie, who seek drama (or possibly divine retribution), who "mislead the pure", who "sin just for fun", and so on. Wonder says "they won't go when I go" -- possibly meaning they won't go to Heaven. But in that case it ought to be "They won't go where I go", so your guess is as good as mine. Although, in the final stanza, you have "The kingdom I will see". "Kingdom" pretty much means "Heaven".
Anyway all of that is important to judging what Wonder means by the second of the two lines you quote. The first is pretty obvious, but the second "wanting tragic ends" could mean "people consciously or unconsciously seeking death" or it could refer to judgmental people who want tragic death for other people. Or it could just mean people who want things that will lead to general tragedy.
I don't think it much matters to the overall theme of the song, which again, seems to me a gospel tune about how the righteous will go to Heaven.