Imam Ar-Ridha’ (a.s.) said:
اِنَّما قُلْنا «الَّطِيفُ» لِلْخَلْقِ اللَّطِيفِ... وَ ما لا يَكادُ عُيُونُنا تَسْتَبِينَهُ لِدِمامَةِ خَلْقِها، لا تَراهُ عُيُونُنا وَ لاتَلْمُسُهُ اَيْدِينا!
We say God is All-subtle due to His creation of very fine, minute creatures; so small that we cannot see them and our hand does not feel them.1
What you see above is a small part of a long tradition which Fat’h Ibn Yazid Gorgani has narrated from Imam Ar-Ridha’ (a.s.), in which it is described that ‘these animals are so tiny that they are never felt, and are scattered among the waves of the seas and barks of trees, and deserts and plains’.
This is a miraculous tradition from our Imam dating back about one thousand years which means hundreds of years before the discoveries of microbiology founder Louis Pasteur (1822-1895 AD).