Snippet collections in English translation. These tend to be organized by passage. For example,
More than one period:
Reformation / Early Modern:
Snippet collections in the original. These tend to be organized by passage. For example,
Patristic period (there are also various catalogs--as distinguished from full-text collections--of these, just for example in Clavis patrum graecorum 4 and the 3rd edition of Clavis patrum latinorum):
Here are three examples of Scripture indices, the first from the Mourant & Collinge translation of Augustine's Four anti-Pelagian writings (FC 86), the second from the Corpus Christianorum edition of the Sermons of Peter Damien (CCCM 57), and the third from the Index to the whole of Luther's Works (American edition). (Prefer, however, indices to the full-blown critical editions in the original languages, as these are likely to be the most complete.)
Patrologies, handbooks, and period- or discipline-specific serial and non-serial bibliographies should be used to turn up snippets of commentary published in the form of articles in journals or books, and theses or dissertations. Here is an example of a (comparatively extensive) sermon on Jn 14:28 that I turned up in the handbook or non-serial annotated bibliography entitled the Handbook of patristic exegesis:
Serial bibliographies for the Patristic and Medieval periods are listed under Find (Commentary in) Articles, Patristic and Medieval; those for the Reformation and Early Modern periods are listed under Find (Commentary in) Articles, Reformation / Early Modern.