The central message of this sermon is that true spirituality is not just about intellectual understanding or external practices, but rather it is demonstrated by one's behavior, specifically through their speech and actions towards others. The sermon presents two tests of "pure religion": the first being control over one's tongue, implying a tight rein on one's words to ensure they align with God's character; the second being compassion, which involves showing kindness and concern for others in need. These tests reveal that true spirituality is not about appearances or external rituals, but rather it is about how one treats others and demonstrates God's love through their actions. The sermon advances the belief that faith is not just a mental assent, but it must be lived out practically through one's words and deeds. The takeaway for listeners is to evaluate their own spirituality by examining their speech and compassion towards others, recognizing that true purity of heart is demonstrated by consistent obedience to God's character.