Question: Is it not taqwa to abstain from eating food about which one doubts whether it contains lard or alcohol and from meat that one does not know how it was slaughtered?
It is not taqwa (piety), but waswasa (Satanic whisperings) and a sin. Hadrat ‘Umar said, “We abstained from nine-tenths of permitted things out of fear that we might fall in forbidden things.” This statement is about the other forbidden things, not about what you have mentioned in the question.
Hadrat Imam-i Ghazali states, “You should also refrain from things that may be haram, because it was stated in a hadith-i sharif, ‘One who abstains from doubtful things has protected one’s religion and chastity. One who goes around doubtful things may fall into haram.’ However, it is not taqwa, but waswasa, to be doubtful about food and drink and to refrain from them. For example, our religion commands, ‘Eat that which is not known whether haram or not.’ [Maybe it is haram, but it is not sinful to eat it as we do not know.] Our religion does not command, ‘Do not eat that which is not known whether haram or not,’ because it is impossible to determine it. As our religion does not order us to search, our Master the Prophet made wudu' from the jug of a polytheist, and Hadrat 'Umar made wudu' from the jug [maybe it was impure] of a Christian. The Blessed Companions used to drink the water non-Muslims gave and buy meat, cheese, etc. that they sold. In fact, it is haram to eat that which is impure. Generally, disbelievers are dirty, and there are smears of wine on their hands and utensils. They slaughter animals without mentioning the Basmala over it. In spite of these facts, the Blessed Companions used to eat such foods as they did not know for sure whether they were impure or not, so they did not act upon waswasa” (Ihya).
Hadrat Imam-I Qastalani states:
After our Master the Prophet, together with the Blessed Companions, had had a bite of poisonous food served by a Jew in Khaybar, he said, “This meat said to me that it was poisonous” and he did not eat any more. He said during his last disease, “I still feel the pain caused by the meat I ate in Khaybar.” (Mawahib)
Our Master the Messenger of Allah ate a Jew’s bread and meal that contained butter and he did not ask whether they were pure. He did not ask whether it contained lard or sheep fat or whether the bread contained water or wine. He made wudu' from the water jug of a polytheist woman. Each is a proof that there is no need for a search.
Hadrat Imam-i Rabbani states:
What is impure is not the bodies of disbelievers, but their
faith. It is stated in the Qur’an al-karim (what means), “It is lawful to eat what the People of the Book [Jews and Christians] cook [and slaughter].” (Al-Ma’idah 5)
Do not think the Muslims who have dealings with disbelievers to be dirty, and do not refrain from their food and drink. What is caution is not to abstain from the food and drink of disbelievers, but to save oneself from this state. (Volume 3, Letter 22)
Disbelievers may mix impurity and even poison into our food, just as in the example of the Jew. Our Master the Prophet ate the meal without inquiring because it is waswasa, not taqwa, to refrain from the food that is not known whether pure or impure. Our religion orders us to stay away from waswasa. (Hadiqa)
The general rule is that a thing is assumed pure. It is not assumed impure due to doubt. Therefore, it is not necessary to inquire about something whether it is pure or not. When Hadrat Amr bin As asked the owner of the poor, “Does a beast come into your pool?” Hadrat ‘Umar did not allow him to answer saying, “Mind you do not answer.” Accordingly, it is not permissible for a guest to ask the host whether the food offered is impure or not. (Ni’met-i Islam)
In our religion, there is a rule, “No proof is needed for something to be halal. Proof is sought for something to be haram.” If no proof is found as to whether something is impure, it is assumed pure. (Usul-i Pazdawi)
If impurity is mixed into margarine, sausage, beverages, or any other food but if this fact is not known, it is permissible to eat it. Knowing it happens by way of either seeing it in person or by the testimonies of pious (adil) Muslims that they have seen people mixing impurity into it. Saying “We hear that impurity is mixed” does not render something haram. (Ashbah)
Lard may be mixed into soap. However, when impure fat or lard is made soap or wine turns into vinegar, it becomes pure. It is true for all chemical changes. (Tahtawi)
Question: Is it permissible to abstain from any food and not to eat it with the thought that it may contain impurity?
It is waswasa, delusion, and harmful to abstain from something without knowing for certain that it is impure. (Kimya-i Sa’adat)
Question: Is the testimony of a non-Muslim or a sinner or an innovator accepted if he claims that something is haram?
No, what a non-Muslim or a sinner or an innovator (ahl al-bid'ah) says in the matters of the religion is not accepted, even his recitation of the adhan. It must be recited again.
In the matters of the religion, only the statement of an adil Muslim is accepted. The statement of a sinner has no credibility about qiblah direction, purity and impurity, or permissibility and prohibition. (Radd-ul- Mukhtar)
Innovators (ahl al-bid’a) are not considered adil even though they are ahl al-qiblah and do all acts of worship. (Hadiqa)
Therefore, testimony of an ordinary person is not credible. First, one must have the faith of Ahl as-Sunnah wa'l Jama'ah, and then one must not be a sinner, but an adil Muslim. Even if a non-Muslim or a sinner or an innovator makes an analysis and writes a report or shows documents, his statements and testimony in the matters of the religion are invalid. however, it is permissible to trust them in other matters.