[Line 1] Late came the God: The unnamed pagan god is presumably the Greek Eros, son of Aphrodite, the goddess of love (known to the Romans as Cupido, and Venus). His unregarded forerunners refer to the earlier, unsuccessful attempts by Cupid’s minions to make the woman fall deeply in love.
[Line 3] The contempt be rewarded: She has incurred the anger of Eros, since the gods, as everyone knows, resent cocksure self-confidence.
[Lines 5 and 6] He poisoned the blade and struck home etc.: I cannot help feeling that, when he wrote these lines, Kipling must have had in mind Bernini’s famous Baroque sculpture representing The Ecstasy of St Teresa, which shows an angel in the act of piercing the saint’s bosom with a fearsome javelin.
[Line 7] He made treaty with Time to stand still: so that time would not heal her wound.
[Line 9] midnights unslaked for her: To slake is to satisfy or quench one’s desire or thirst. Her midnight desire for the man she loved would not be slaked.
[Line 10] Till the stones of the streets of her Hells and her Paradise ached for her: a difficult line, until one realises how closely the poem is based on the story, in which, remembering the time when Harry was still in love with her, Mrs Ashcroft says that “’E was me master, an’—O God, help us!—we’d laugh over it walkin’ together after dark in them paved streets, an me corns fair wrenching in me boots!” (Page 123, lines 1-2) Also, looking for him to come back after he had left her, “Goin’ over the streets we’d used, I thought de very pave-stones ’ud shruck out (would shriek out) under me feet.” (ibid., lines 29-30) So the same streets have been her Paradise and her Hell, and her pain is so intense that she imagines it imparts itself to the stones. The God to whom she appeals for help, in what may only be a commonplace exclamation, may also be the God of the poem.
[Line 10] till the stones … ached See Luke 19.39-40:
And some of the Pharisees from among the multitude said unto him, ‘Master, rebuke thy disciples’.
And he answered and said unto them, ‘I tell you that, if these should hold their peace, the stones would immediately cry out.
The parallel is even stronger with the prose passage quoted in your site’s note on this line. [D.H.[
[Line 12] she called on the Night for a sign More biblical language: S ee e.g. Isaiah 7.10-11:
Moreover the Lord spake again unto Ahaz, saying, ‘Ask thee a sign of the Lord thy God; ask it either in the depth, or in the height above’);
Then certain of the scribes and of the Pharisees answered, saying, ‘Master, we would see a sign from thee’. But he answered and said unto them, ‘An evil and adulterous generation seeketh after a sign; and there shall no sign be given to it, but the sign of the prophet Jonas’.
1 Corinthians 1.22:
for the Jews require a sign, and the Greeks seek after wisdom. [D.H.[
[Line 23] builded an altar The phrase, or similar ones (“builded the altar”, etc), are found at Genesis 8.20, 12.7-8, 26.25; Joshua 22.16; Exodus 24.4; Ezra 3.2 [D.H.[