When choosing more than one preaching text for a single sermon, it is more important to look for the repetition of motifs, type-scenes, and theological themes than the repetition of words.
A motif is the repetition of a tangible object, image, or action within a narrative that imports symbolic and thematic significance. A motif lacks any significance until it is compounded by repetition in several related preaching texts. For example, the motif of clothing is prevalent in the Joseph novella of Genesis 39-50. Any isolated mention of clothing is easily overlooked. However, the compounded discussion about clothing alerts the preacher to possible connections within the broader canon.
A type-scene is the predictable repetition of a particular literary structure in more than one passage or story. According to Robert Alter (The Art of Biblical Narrative, 49), type-scenes are identified by observing the “perplexing fact that in biblical narrative more or less the same story often seems to be told two or three or more times about different characters, or sometimes even about the same character in different sets of circumstances.” A type-scene can be identified by the recurrence of a fixed pattern of motifs, speech, or behavior in parallel situations. For example, Isaac (Genesis 24), Jacob (Genesis 29-30), Moses (Exodus 2), and Jesus (John 4) all have intriguing interactions with women at a well, each unfolding according to a predictable plot sequence. Connecting these preaching texts will yield a harvest.
A theological theme is a definitive reality about God and His involvement in history. More important than the repetition of the word deliverance, for example is the theme of exile and deliverance weaved throughout the Bible.
Of course, the safest way to link any two or more passages of Scripture is to look for specific and explicit reference in one passage to another. However, this need not be the only way since there are many allusions created by motifs, type-scenes, and theological themes throughout the Bible. These deeper connection points are more valuable to the preacher than a simple word study, though word studies can be valuable when performed responsibly.