Jesus and the Old Testament
Jesus put his stamp of authority on the Old Testament. He treated its historical narratives as straightforward records of fact. Interestingly the stories that are the least acceptable to the 'modern mind' are the very ones he seemed most fond of choosing for his illustrations (eg. Abel (Mt 23:35), Noah (Lk 17:26-27), Jonah (Mt 12:39-41)). He repeatedly quoted it as the final court of appeal in debates, not only with his earthly opponents but with the Devil himself (Mt 4:1-11) He believed its prophecies were fulfilled in him (Lk 24:44) and used them as proof of his claims to be the Messiah (Jn 4:25-26; Mt 16:20) and he obeyed its ethical teaching (Mt 5:17-21; Mt 23:23; Jn 8:46).
Jesus commanded his disciples to obey the teachers of the law in so far as they were faithful to the Law of Moses (Mt 23:2-3), and said that anyone who broke one of the least of the Law's commandments and taught others to do the same would be called least in the Kingdom of Heaven. Not 'the least stroke of a pen' is to disappear from the Law until 'heaven and earth disappear'. In fact his disciples are expected to go beyond mere observance of the letter of the Law to fulfilment of the very principle of love upon which it is based (Mt 5:17-20). So for example, in the eyes of Christ, hate and lust are to be regarded as seriously as murder and adultery (Mt 5:21-22, 27-28). Jesus had a very high view of the Old Testament.
Jesus and the New Testament
Jesus commissioned the writing of the New Testament. We can be confident that what the Apostles recorded was what Christ said (Lk 1:3; Jn 20:30-31; 2 Pet 1:16), not only because they were eyewitnesses of all that he said and did but more importantly because he personally commissioned them and gave them the authority to teach in his name (Mt 28:19-20; Gal 1:11-12; Mt 16:18-19; 18:18). The fact that what is recorded in the New Testament is the testimony of eye-witnesses means that we can be confident that there were not errors of a 'Chinese-whisper' type that have crept into the text.
We have not only the apostles' testimony themselves that what they wrote were the words of Christ but also Christ's own testimony that he would enable them by means of his Holy Spirit (Jn 14:25-26) to 'teach them all things', 'remind them of everything he said', 'take what was his and make it known to them' and 'guide them into all truth' (Jn 16:12-15).
It is true that we are now 'not under law but under grace' (Rom 6:14) but this refers to the basis of our justification rather than our ethical obligations. Under the New Covenant, God's laws are written on our hearts (Je 31:33; Ezk 36:25-27) and we are now enabled and exhorted to live 'according to the Spirit'. In other words , while our goodness or righteousness is 'by faith' (Rom 1:17) the evidence of the genuineness of our faith is that we perform good works (Jas 2:26) by being conformed to Jesus Christ.
The Sufficiency of the Bible
The Bible is God's Word to us, coming to us with the very authority of Christ and given in order that we may 'be thoroughly equipped for every good work'. It is sufficient (2 Tim 3:16,17). There are accordingly very stern warnings in the Bible about adding to or subtracting from what God has already revealed (Dt 4:2; 12:32; Pr 30:6; Rev 22:18-19). A logical corollary of this is that we should share Jesus' own high regard for the Scriptures. We will want regularly to hear, read, study and meditate on what God has revealed in the Old and New Testaments so that our thoughts and actions will be increasingly in line with those of Jesus himself.
Here we must be careful not to fall into one of three traps. Loving as Christ loves is not legalism, a slave-like obedience where the letter of the law supplants the spirit. This was the mistake of the Pharisees(Mt 23:23-24). Nor is loving as Christ loves antinomianism where the commands of God are simply dispensed with (Rom 6:15). The Christian life is one of obedience. Nor is loving as Christ loves situationism, where the situation determines the action. Christ's life was a fulfilment of the law (Mt 5:17-20). Let's consider each of these in turn.
Antinomianism dispenses with law altogether. The antinomian argues that since we are under grace , and not law, and since the death of Christ cleanses us from all unrighteousness, we are no longer under any obligation to obey the moral law. This flies in the face of Paul's own rhetorical question 'Shall we sin because we are not under law but under grace?' to which he supplies his own answer 'By no means!' and goes on to point out that our freedom from the condemnation of the law means that we are now 'slaves of righteousness' and thereby obliged to obey God's commands (Rom 6:15-18).
Situationism retains the law but claims that in certain situations the commandments may be suspended in favour of the higher principle of 'love to one's neighbour' (Mt 22:39-40). The situationist argues that one may intentionally kill in certain situations and yet be acting 'in love'. There are two main problems with this. Firstly it clearly contravenes Christ's own teaching that obedience to the greater commandments of the law does not in any way excuse disobedience to the lesser (Mt 5:17-20, 23:23). In the mind of Christ these 'conflicts of duty' simply do not occur. Secondly it begs the question of what a 'loving' action is. The reality is that 'individual conviction or conscience' is made the arbiter of right and wrong, a return to ancient heresy of each doing 'as he sees fit' (Dt 12:8). This has tremendous dangers as we have already seen with our forgoing historical outline.
Legalism substitutes human oral tradition for God's law and introduces a nonbiblical hierarchy of sins (Mk 7:8-13). God's true commandments are distorted such that they become impractical and in fact impossible for all but a select group to obey. Thus the prohibition against 'intentional killing of the innocent' may become a directive to 'strive officiously to sustain life at all costs'. The result is that the most important principles of love, justice and mercy are ultimately lost sight of and a new law is imposed (Mt 23:23). A tragic consequence can be that in the case of terminal care the attainable goals of caring, consoling and comforting are forgotten as the doctor driven more by guilt than compassion feels he must do everything technologically possible for the patient.
Antinomianism, Situationism and Legalism are all distortions of Christian teaching, in short they are heresies with dangerous consequences and need to be recognised as such and rejected. However we need to recognise that each is in part an overreaction to mistakes of the past: antinomianism to joyless obedience, situationism to obedience without compassion and pharisaism to lawless indulgence. In rejecting these false 'isms' we need to recognise that the best argument against them is the practical demonstration of joyful, compassionate, obedient Christian service.