There are several ways God commands us. There are direct commandments and indirect commandments. Jesus tells us specifically, unless we repent we will perish.
Indirect commands come in a variety of forms, but the most common is the commandment by exclusion.
Where God has spoken we may speak, where God has not spoken we must remain silent. To begin, let me point a couple verses. We are to speak as the Oracles of God, not of our own mind or intellect but do exactly what God commands. To obey is better than sacrifice, and to heed is better than the fat of rams. For rebellion is like the sin of divination and arrogance like the evil of idolatry.