"The Pulley" is a poem about God's love for mankind and His concern that man is never separated from Him. According to Herbert's narrative, which is interspersed with God's own direct speech, God, at the beginning of creation, blessed man with the "world's riches" poured from his "glass of blessings". These are named in the second stanza as "strength", "beautie", "wisdome", "honour", "pleasure", in that order, except one, "rest" which lay in the bottom of his glass. This visual image of "a glass of blessings" demonstrates God's benevolence. The meaning of the poem is basically anchored on the word "rest" whose several meanings constitute the literary device called "pun", loosely defined as "a play on words". Indeed the first pun on "rest" gives it the meaning of contentment. From God's own perspective, if He should bestow 'rest' on His creature, man, the latter's contentment alone will separate him from God and he will "rest in nature, not the God of nature", and thus "adore my gifts instead of me". Here a related meaning of 'rest' is being played on, which is "abide in", alongside being "content with".
The second pun on "rest" invests the word with the meaning "other(s)" referring to the "worldly riches" God has already bestowed on man. By withholding the gift of "rest" God, nevertheless intends that man should enjoy "the rest" — His other gifts, yet 'rest' withheld generates restlessness in man, its exact opposite. This time, the pun on "rest" includes its opposite — restlessness. The latter is reinforced by God's choice of modifier, — "repining" to produce "repining restlessness".
The implication or suggestion is that God goes to great length to draw man back to Himself (as a pulley does) by creating in the latter an ennui that is never satisfied. This is the result of the "rest" that God withholds from man among the rest of the gifts bestowed. God's arrangement then ensures that if man's inclination to do good does not bring him close enough to God, "weariness" induced by "repining restlessness" will "toss him to my breast". It can be concluded then that pun plays a crucial role in unravelling the meaning of the poem.
Points to note:
(1) The interpretation of pun and its relevance to the theme.
(2) Pun on 'rest' as contentment.
(3) Pun on 'rest' as remainder/other.
(4) Relationship of 'rest' to the thematic concerns of the poem.