The principle that God knows even the thoughts of our hearts is widespread in the scriptures. In modern days the Lord has said: “Behold, I say unto you, my servants Ezra and Northrop, open ye your ears and hearken to the voice of the Lord your God, whose word is quick and powerful, sharper than a two-edged sword, to the dividing asunder of the joints and marrow, soul and spirit; and is a discerner of the thoughts and intents of the heart” (D&C 33:1).
In the Old Testament, Yahweh assured Solomon, “The Lord searcheth all hearts, and understandeth all the imaginations of the thoughts: if thou seek him, he will be found of thee; but if thou forsake him, he will cast thee off for ever” (1 Chr. 28:9).
In biblical language, the heart is the seat of thought, rather than serving as the seat of emotion as in contemporary Western symbolism. In the heart are “true thoughts” stored; thus, knowing one’s “heart” and knowing one’s thoughts are the same thing.
Culture: Because the Almaites had to change from vocal prayer to silent prayer, it suggests that they had a practice of praying aloud in a communal setting. It is this communal prayer that Amulon forbids, though it clearly might extend as well to any individual vocal prayer. This ban had more behind it than simple vindictiveness. By forbidding the communal prayer, Amulon also disrupted other possible communal responses, such as organized resistance. By removing an occasion when the people were unitedly lamenting their fate and asking deliverance, Amulon removed a possible threat to his dominance, as he supposed.
As Mormon notes, the prohibition against public communal prayer did nothing to prevent the silent prayers of these righteous people.