It is related that an Arab who was a huntsman had caught a land-crocodile, which he was carrying to his house as food for his family and children. While he was on the way, he suddenly perceived a large gathering of people and asked for the cause of it. The people replied "Muhammad, the son of 'Abdullah (Sallallahu 'alayhi wa sallam) is here and claims to be a prophet." The Arab forcibly entered the crowd, went up to Muhammad, and said "Ya Muhammad, I shall not believe you until this crocodile believes," and threw the land-crocodile at Rasulullah's feet; but it wanted to run away; therefore his holy and prophetic lordship (Sallallahu 'alayhi wa sallam) exclaimed "Lizard, approach." The animal obeyed, replying in eloquent and distinct language "I await your commands with pleasure." His lordship asked "Whom worshippest thou?" The animal replied "I worship Allah, whose throne is in heaven whose dominion is on earth, whose power is in the sea, whose mercy is in paradise, and whose punishment is in hell." Rasulullah asked, "Who am I?" The animal said, "You are the Rasul of the Lord of both worlds and the seal of Prophets; blessings be on you! Whoever believes you will be saved, and whoever accuses you of falsehood will be damned." When the huntsman heard these words of the crocodile he took the finger of astonishment between the teeth of meditation, and said "After this I wish for no other proof of your veracity. I testify that there is no god but Allah, and I testify that you are His servant and his Rasul. This profession I now make externally and internally. I swear by Allah that when I first approached you, there was no man on the face of the earth whom I hated more than you' now, however, I love you more than my own eyes, ears, father, mother, and children. His holy and prophetic lordship (Sallallahu 'alayhi wa sallam) replied, "Thanks and praises be to Allah, who has shown you the right way."
Source: From Rawza Tas-Safa by El-Shaykh Syed Mubarak Ali Al-Jilani Al-Hashmi