During the time of the Prophet there was no such science as that of jurisprudence. The only ideal for them was the conduct of the Prophet. They learnt ablutions, saying prayers, performing Hajj, etc. by observing the Prophet's actions under his instructions. On occasion, cases were brought to the Prophet for his decision. Prophet's decisions were taken as models for similar decision in similar cases.
The companions occasionally asked him questions relating to certain serious problems, as we learn from the Qur'an the Prophet gave suitable replies to them. People in his lifetime were not interested in unnecessary philosophical discussions or in meticulous details. The Companions generally asked the Prophet very few questions. On one occasion when some person put unnecessary questions to him, the Qur'an asked the companions to desist from doing so. The result was that the Sunnah remained mostly a general directive, interpreted by the early Muslims in different ways. People did not know the details of many a problem even in the lifetime of the Prophet.
Of course the Prophet laid down certain regulations, but the jurist elaborated them with more details. The reason for this further addition to the laws by interpretation is that the Prophet himself had made allowances in his commands. He left many things to the discretion of the community to be decided according to a given situation.
Law was neither inflexible nor so rigidly applied in the early days of Islam. Different and even contradictory laws relating to many problems could be tolerated on the basis of argument. It seems that the Prophet provided a wide scope for differences by giving instructions of a general nature, or by validating two diverse actions in the same situation. The Prophet aimed at providing opportunities for the employment in diverse circumstances. Had the Prophet laid down specific and rigid rules for each problem the coming generations would have been deprived of exercising reason and framing laws according to the need of the hour.
Hence, in Prophet's times, it was possible for two persons to take different courses in one and the same situation. For example, on the occasion of the battle of Banu Qurayzah, the Prophet sent some of his companions to their territory and asked them to say Asr (afternoon) prayers on arrival at their destinations. But it so happened that the time of the prayer came on the way. Therefore some of the companions said their prayers on the way arguing that the Prophet had not meant to postpone the prayers, while others said their prayers on reaching the destination at night-fall, taking the Prophet's command literally. When the incident was reported to the Prophet, he kept silent. The Companions deemed this to be a tacit approval of the actions of both the parties. Had the actions of either party been considered unlawful, it is argued, the Prophet would have pointed out and corrected it.
This example shows that the Prophet while laying down a law, primarily considered the value and spirit of the action and not the form of the action itself. In this case both the parties exhibited their allegiance to God. One of them obeyed the Prophet's command taking it literally and performed Asr prayers at night fall, while the other obeyed him in spirit. This shows that a commandment is not intended per se; what counts is intention and the spirit which constitutes the allegiance to God and the Prophet. This also implies that people can differ in the form of obedience on the basis of interpretation. Hence differences arose in law among the jurists.
After the death of the Prophet the Companions were spread out in different parts of the Muslim world. Most of them came to occupy the positions of intellectual and religious leadership. They were approached by the people of their regions for decisions regarding various problems. They gave their decisions sometimes according to what they had learnt and retained in their memory from the commandments of the Prophet; at other times according to what they understood from the Qur'an and Sunnah.
The interpretation of the Qur'an also caused differences of opinions among the Companions. The points on which the Quranic injunctions were either silent or ambiguous were to be explained. The result was that these verses were sometimes interpreted in the light of traditions from the Prophet, and sometimes on the basis of the jurists' opinions. Moreover since traditions themselves were diverse the differences were natural. Sometimes two contradictory traditions were reported from the Prophet. Some Companions followed one, and some followed the other.
In some cases, a Hadith was not known to a Companion; hence he decided the problem on the basis of his own opinion. When the relevant Hadith was brought to his notice, he withdrew his personal judgement. On this account Umar, the second caliph, changed his opinion several times.
On certain occasions it so happened that the relevant Hadith was available but the reporter himself could not understand its real import. Ibn Umar is reported to have narrated a Hadith from the Prophet that a deceased is punished on account of the mourning of his relatives. When this tradition reached Aisha she rejected it saying that Ibn Umar might have been mistaken or he might have forgotten some relevant part of the tradition. She also observed that the Hadith reported by Ibn Umar goes against the Quranic verse: No soul bears the burden of another.
The Companions, however, tried their best to base their decisions on the Quran and Sunnah. They aspired to keep their decisions and personal judgements as much close to those of the Prophet as possible. Despite their differences, they did not deviate from the spirit of the Qur'an and Hadith.
The Successors took their stand on the opinions expressed by the Companions. They retained in their memory the hadith of the Prophet and the opinions of his Companions. They made attempts to reconcile opposite opinions held by the Companions on many problems. The Successors exercised ijtihad in two ways. First, they were not afraid of giving preference to the opinions of one Companion over another and sometimes, even the opinions of a Successor over those of a Companion. Secondly they exercised original thinking themselves. In fact, the real formation of Islamic law starts in more or less professional manner at the hands of the Successors.
With the Successors, the Islamic law began to take its formal shape and develop into an independent subject of study. In this age the principles which governed fiqh were the Qur'an, Sunnah and Qiyas (deductive reasoning). These principles were introduced by the Prophet himself.
Whenever any problem arose the Muslims tried to solve it by first referring to the Qur'an; if no definite answer was found in the Qur'an then they would turn to the Sunnah; if there too the problem remained to be solved then they resorted to consensus of the scholars; and as a final recourse they drew an analogy with the Qur'an and Sunnah.
Here is an example of how an analogy is drawn. For instance alcoholic beverage is prohibited in the Qur'an, but there is no mention of hard drugs. Since alcohol is prohibited because of its intoxicating effect and since hard drugs generate a similar effect, then by analogy (qiyas) hard drugs are also prohibited.
As we have seen above, the science of jurisprudence had come into existence with the advent of Islam, but it developed as a regular discipline in the second century A.H. Abu Hanifa has played the leading role in this gigantic task of compilation and systematization of the Islamic Law.
When after the conquests, and with a large number of converts, Muslims came into contact with different cultures and civilization, they were faced with new situation. To deal with these new situations it became necessary to devise specific rules and detailed directions from the broad principles practised so far. For example, if a person inadvertently omitted some part of the ritual of prayer, the question arose as to whether his prayer was valid or not. It was not practicable to declare everyone of the actions in the prayer as imperative. Therefore the actions were divided into different grades such as fard, wajib, masnun and mustahab. Differences of opinion arose as regards the criteria to be adopted for this grading. In deciding such questions the scholars took recourse to deduction, analogy and conjecture, in which they followed different method.
The first compilation of Fiqh ruling, a short collection in Abraham Nakhai's time consists of Fatwas of Ali and Abdullah ibn Masu'd. This was not a systematic compilation. It was in the possession of Hammad who died in 120 AH and was succeeded by Abu Hanifah.
Although by Abu Hanifah's time the accepted rules of fiqh had not been collected, they existed in the form of oral traditions. These had not been systematized into a regular discipline. There were no methods of reasoning, no rules for the derivation of orders, no grading of Traditions, and no principles of analogical deduction. Fiqh had a long way to go before becoming a system.