The Arabic term taklīf is derived from the term kulfah which means difficulty. It is used to mean the forcing of an action. For example the sentence; Zayd forces (kalafa) ‛Amr to do an action; he forces him.
Divine laws are called taklīf because they are sent from the Master, glory be to him, and it is necessary for the mukalaf to obey them.
So, taklīf means a forced action given to an adult by the Master, glory be to him. These actions encompass different aspects of man's life, for example his personal life, his worship, his family life and his social life. These laws give order to his life. Examples of these laws are: prayer being obligatory and adultery being forbidden.
From the beginning of Islam until its middle ages there was another word for fiqh, it was ijtihād.
Ijtihād is derived from the term juhd which means effort and struggle. The jurist is called a mujtahed because of his efforts and struggle in making religious rulings.
The word istanbāt) has a similar meaning. It is derived from the word nabat) (al-mā') which literally means taking water out of the ground. A jurist performs a similar action when he struggles to take the religious ruling from its source.
The term ijtihād is used by the religious scholars to mean obtaining a proof for a religious ruling.
The Necessity of Ijtihad
Islamic rulings are not mentioned for every situation. That would be impossible, because there are countless situations that happen all the time. Instead it gives general principles and rules.
So, when a jurist must make a ruling for a certain situation he must look into the official sources and give his ruling. Here is where fiqh is synonymous with a deep, precise and inclusive understanding.
Definition: a mujtahed is one who has reached the level of ijtihād in understanding religious laws. This means that he has the ability to deduct religious rulings from the Qurān and traditions.
This mujtahed is able to deduct religious laws in all the subjects that the mukalaf needs or only certain subjects because of their ease. In the first case he is called a pure mujtahed and in the second case a minor mujtahed.
The sciences that a mujtahed needs to know in order to be able to deduct religious rulings are:
1. Arabic grammar; syntax, morphology, vocabulary and eloquence. The reason for this is that the Qurān and traditions are in Arabic and it is impossible to understand the Qurān or the traditions without knowing Arabic.
2. Tafsīr; the mujtahed will have to refer to the Qurān so he must have a general knowledge of tafsīr.
3. Logic; because every deductive skill needs logic. Logic teaches one how to define something and how to deduce something.
4. The science of traditions: a mujtahed must know about traditions and their categories.
5. The science rijāl: This is the science of knowing the people in the chains of narrations; knowing if they are trustworthy or not. The reason for this is that one cannot accept everything that is narrated unless it is narrated by trustworthy people.
6. The principles of jurisprudence: This is one of the most important sciences that the mujtahed must know because they are the rules that are applied in all of the different sections of jurisprudence.
Taqlīd means acting according to the verdict of a mujtahed. Taqlīd shifts the responsibility of finding the religious ruling from the person performing taqlīd to the mujtahed.
Taqlīd is one of the ways of finding a religious ruling, like ijtihād. Except that ijtihād is a direct way and taqlīd is an indirect way, because one reaches the religious ruling from the ijtihād of another.
The proof for taqlīd being permissible or obligatory is the actions of sane people. Sane people find it necessary for an ignorant person to refer to a scholar. The referral of the ignorant to the scholar is something seen in every society that man has been in. It is even seen today. An example of it is when a non-specialist refers to a specialist.
One is dependant on taqlīd in finding out religious rulings except in the cases where one knows a religious rule. One can know a religious rule by having certainty about it which is possible without struggling and without study. Examples of these are some of the obligatory actions, many of the recommended actions and most of the permissible actions which are known by most of the people who live in religious areas. Or, one can know the religious rule because of it being self-evident like the obligation of prayer or the forbiddance of drinking wine.
Precaution means: the mukalaf performing everything that he suspects to be obligatory but does not suspect it to be forbidden or refraining from performing anything that he suspects to be forbidden but does not suspect it to be obligatory. The mukalaf must know the different instances of precaution to be able to do this. He must know every place where it is suspected to be obligatory and not suspected to be forbidden or it is suspected to be forbidden and not suspected to be obligatory. This knowledge does not come without looking at verdicts from different mujtaheds.
So, precaution is another tool of finding the religious ruling. It is different than the previous two, ijtihād and taqlīd. The mujtahed reaches the religious ruling from his efforts while the person who performs taqlīd obtains the exact rule from the mujtahed. But, the person who performs precaution only gets a general understanding of the rule. The reason for this is that the religious ruling for him is something dangling between obligation, recommendation or permission.
Precaution is a way of becoming certain that one has performed the real religious ruling. Precaution is divided into two categories:
1. Obligatory precaution: the mukalaf must act according to precaution if he wants to stay on the taqlīd of whoever he performs taqlīd to. But, in this ruling, he can act upon the verdict of another scholar if he wants to change the person who he performs taqlīd to. The condition that must be followed is that he must change from the most knowledgeable to the next most knowledgeable and so on.
2. Recommended precaution: the mukalaf does not have to act according to this precaution, but it is better to do so.
 Muh)ammad Bāqir al-S)adr, H)alaqah 1, page 126
 Shahīd Mut)t)aharī, Makhul Ila al-‛Ulūm al-Islamīyyah, page 10
 ‛Alī Mishkīnī, Is)t)alāh)āt al-Us)ūl, page 18
 Shahīd Mut)t)aharī, Makhul Ila al-‛Ulūm al-Islamīyyah, page 8
 Hādī al-Fad)lī, Dūrūs fī al-Fiqh al-Imāmīyyah, page 39
 Hādī al-Fad)lī, Dūrūs fī al-Fiqh al-Imāmīyyah, pages 252-254
 Hādī al-Fad)lī, Dūrūs fī al-Fiqh al-Imāmīyyah, pages 255-256