1.  "milk of human kindness"     b.  Macbeth
Lady Macbeth worries about her husband's better nature in Macbeth (I.v.17).

2.  "more sinned against than sinning"     e.  King Lear
Lear sees himself in this unfortunate circumstance in King Lear (III.ii.60).

3.  "salad days"     a.  Antony and Cleopatra
Cleopatra recalls "My salad days, / When I was green in judgment, cold in blood" in Antony and Cleopatra (I.v.73-74).

4.  "strange bedfellows"     c.  The Tempest
Trinculo, a jester in The Tempest, uses this expression about misery (II.ii.40); in 1870, the American editorialist Charles Dudley Warner added a familiar twist in writing, "Politics makes strange bedfellows."

5.  "loved not wisely but too well"     d.  Othello
In Othello, the title character speaks these words in describing his own predicament before killing himself (V.ii.344).