This introductory essay overviews the indispensable theme of Christ’s penal substitution on Golgotha’s cross. The subject unfolds in two parts; the first section provides background and context for this essential theological truth. The second section reasons that three compelling biblical necessities require a true believer in Jesus Christ to understand scripturally and accept the Savior’s penal substitution on behalf of redeemed sinners, especially oneself. The landscape/backdrop for this article provides (1) a definition of “Christ’s penal substitution,” (2) statements by representative defenders and objectors to this doctrine, and (3) an introduction to subsequent and more focused writings in this issue of TMSJ. Then follows the proposition that Scripture must necessarily be understood as consistently (in both OT and NT) teaching Christ’s penal substitution, which rests on three convincing biblical lines of thinking: (1) revelational evidence, (2) lexical evidence, and (3) theological evidence. The writer thus concludes that this teaching is clear, not obscure, thoroughly biblical, not humanly contrived, and essential to personal salvation, not optional.