How can a man lend his money in a halal way without writing or having witnesses, taking into account the noble Hadith: "There are three whose prayers God does not answer... and a man who had money owed to him by another man, but he did not have witnesses for it"?

Divine revelation guided us to the writing down of debt and taking witnesses for it in Surat al-Baqarah, verse 282. Scholars differed regarding the ruling on this; some held it to be obligatory, while the majority held it to be a matter of guidance and recommendation, not obligation. The majority cited evidence from the verse itself (283) indicating that the command is for guidance, and that the owner of the money may waive it, and because the predecessors did not adhere to it as an obligatory commitment.

As for the hadith: "There are three whose supplication Allah does not answer: a man who had a bad-tempered wife but did not divorce her, a man who gave his money to a foolish person... and a man who had a debt owed to him by another man but did not take witnesses for it," it is attributed to Abu Musa al-Ash'ari and not مرفوع (directly attributed) to the Prophet, peace be upon him, and some scholars deemed it weak. Even if it were authentic, the non-answering of supplication does not mean falling into sin; rather, it is a disciplinary measure for one who is negligent in taking the legitimate means to protect their interests.