The holiness of God is meant to motivate us. We are to be holy because God is holy (Lev 11:44ff; 1 Pet 1:15,16). His holiness is an incentive for our own. Yes, the cross is a great motivator for the Christian. So also is the holiness of God. The goodness of God, not just His grace, is also meant to motivate us. Because God causes the sun to shine and the rain to fall on the just and the unjust, we are also meant to be good to all (Mt 5:43-48). Warnings play a significant role in the motivations for obedience throughout the Sermon on the Mount (e.g. Mt 5:21-48; 7:21-23). Both the promise of rewards (Mt 5:3-12; 2 Tim 2:5,6; 4:8) and the threat of punishments (1 Cor 3:12-15; 4:18-21) are valid incentives for Christian living.