A few from the top of my head:

The last few bars of the slow movement from Beethoven's last string quartet.

The chorus "Praise the Lord" from Handel's oratorio "Solomon."

(As much an incidence of track arrangement on a Norrington disk I own) the
Mozart "Requiem" followed immmediately by his "Ave verum corpus."

The two slow arias for soprano in Handel's "Ode to St.  Cecilia":  the
first whose title escapes me now which concerns the lyre; the second "What
art can teach" about the organ.

The passage moving from the Praeludium to the Benedictus with the solo
violin and flutes in Beethoven's "Missa Solemnis."

Georg Muffat's "Chaconne in G major" as performed by the Musica Antiqua
Koln/Reinhard Goebel on their "Chaconne" disc.

Mark K. Ehlert