Hawzah News Agency – The merciful prophet of Islam (pbuh) says:

أصنافٌ لا يُستَجابُ لَهُم، مِنهُم مَن أدانَ رَجُلاً دَيناً إلى‏ أجَلٍ فلَم يَكتُبْ علَيهِ كِتاباً ولَم يُشهِدْ علَيهِ شُهُوداً.

'There are certain types of people whose supplications are not answered. From among them is the man who lends money to someone for a specified time and neither writes it down nor has anyone witness it.'

Source: Bihar al-Anwar, v. 104, p. 301, no. 1