The third stanza picks up on the concluding clause of the second stanza. The second stanza ends with the unfinished idea Thou’lt make me.

The third stanza begins, Thou’lt make me then its fruit

So second through third stanze read:

             Thou’lt make me

Thou’lt make me then its fruit. 

The chaining of the end-beginning clauses creates musical effect of speed, which is not common in Taylor’s often jagged verse. The effect is joyful and expectant. He will become a tree which shall not be moved though wind blow and hell attacks:

Thou’lt make me then its fruit, and branch to spring,
And though a nipping east wind blow, and all
Hell’s nymphs with spite their dog’s sticks therat ding
To dash the graft off, and its fruits to fall,
Yet I shall stand Thy graft, and fruits that are
Fruits of the tree of life Thy graft shall bear.

As explained with respect to the second stanza, the language of graft recalls the letter to the Romans. Here Taylor echoes Psalm 1. The blessed man whose delight is in the law of the Lord:

…he shall be like a tree

Planted by the rivers of water, 

That bringeth forth his fruit in his season;

His leaf also shall not wither;

And whatsoever he doeth shall prosper.

The rhythmic effects are interesting here. Two lines of regular rhythm are jarred by the accent on the first syllable of the third line, 

HELL’S NYMPHS

The enemy thus is emphasized. The fourth line scans

To DASH the GRAFT OFF, and its FRUITS to FALL,

The spondee GRAFT OFF followed by a pause, slows down the line and places emphasis on this attack. The damage is further emphasized in the second half of the line by the alliteration, “fruits/fall” which draws the two words together – but also harkens back to the f in Graft and Off.

The words “graft” and “fruit” then take the foreground in the final lines of the stanza. Notice how the repetition of the words also draws the two words together due to the alliteration of “f”, “r” and “t”:

To dash the graft off, and its fruits to fall,
Yet I shall stand Thy graft, and fruits that are
Fruits of the tree of life Thy graft shall bear.

The work which God does by grafting Taylor into the tree is a work which shall not be lost. This is a picturesque display of the doctrine of perseverance. Simply put, if God does a true work in a heart, that person will not be lost; God will cause them to continue. 

This is the understand of the doctrine of election: It is a comfort: you will not be lost. Unfortunately, it is sometimes raised a barrier: you cannot enter. Taylor puts the emphasis in the right. The tree will be battered; the graft will be tried: but, the graft will stand, because it is God’s work. This is shown in the first line of the stanza:

Thou’lt make me then its fruit, and branch to spring

God’s work will stand. Hell will raise against it, but Hell will prevail.