It is narrated in Tafsir of Imam Hasan Askari(as) regarding words of Allah(swt):
“…..and keep up prayer……………” (Sura Baqara, Verse 3)
Imam Hasan Askari (a.s.) said: Allah Almighty again describes the virtue of those righteous people and says: …and keep up prayer…, meaning they establish prayer and perform bowings and prostrations perfectly and also fully abide by their timings and limits, and refrain from things which make Prayer null and void or render it imperfect.
My ancestors have, quoting their ancestors, narrated to me that once the Holy Prophet’s (s.a.w.s.) close and sincere companion, Abu Tharr Ghaffari, approached the Prophet and said: O Allah’s Messenger! I have sixty female sheep. If I take them for grazing to the forest, I cannot bear separation from your honour. On the other hand, if I hand them over to any shepherd for grazing, I fear he may behave harshly with them and not graze them properly. Kindly show me what I should do to overcome this confusion.
The Holy Prophet (s.a.w.s.) replied: You yourself go and graze them. So Abu Tharr went with his animals to the jungle and returned on the seventh day. The Holy Prophet (s.a.w.s.) asked him: O Abu Tharr! What did you do with your animals? The latter replied: A very strange thing happened. When I was busy performing my prayer, a wolf attacked them. I became perplexed and could not instantly decide whether I should interrupt my prayer or continue it, overlooking the fate of my sheep. Finally I preferred the prayer.
At that time Satan inserted doubt in my heart saying: If the wolf eats up your animals, you will lose your source of sustenance. I told the Satan: In any case my faith in the Oneness of God, in His Prophet, in his cousin Ali (a.s.) and his progeny would remain with me and so also my love and friendship with them and my enmity towards their enemies. So, in such a case, losing and missing every other thing of the world would be easy for me to bear. I continued my prayer.
What I then saw was that a wolf caught hold of a sheep but at the same time a tiger jumped on the wolf and tore it into two pieces, freed the lamb and sent it to its group and told me: O Abu Tharr! Continue your prayer and do not worry about your animals, as Allah Almighty has appointed me to protect them until you finish your prayer. Upon hearing this, I busied myself with my prayer. This surprised me to an extent known only to Allah Almighty. When I completed my prayer, that tiger came to me and said: Go to the Holy Prophet (s.a.w.s.) and tell him: Allah Almighty has given honor to your companion and the protector of your Shariat and has appointed a tiger to protect his animals.
Hearing this event all in the audience were surprised. Then the Holy Prophet (s.a.w.s.) said: O Abu Tharr! I, Ali, Fatima, Hasan and Husain (a.s.) believe in what you said. But those who were hypocrites said: This is the result of a preplanned affair between Muhammad (s.a.w.s.) and Abu Tharr (r.a.). He wants to deceive us in this way.
Twenty of them decided to go and look personally into the reported matter about the sheep. Let us see, they said, whether a tiger really protects the sheep when Abu Tharr is engaged in Prayer. They themselves observed that the tiger was taking rounds near Abu Tharr; that the tiger sends back any lamb to the flock when separated so long as Abu Tharr prays. They themselves saw that when Abu Tharr finished his worship, the tiger called on him and said: Take care of your sheep. They are safe.
Then that tiger addressed the hypocrites saying: O group of hypocrites! Did you deny that Allah Almighty may make me an obedient servant of one who is the friend of Allah, His Prophet, Ali (a.s.) and their progeny and of those who take intercession so that I should take care of his animals? I swear by the Holy Being, Who has given honor and excellence to Muhammad (s.a.w.s.) and to his purified progeny and declare that Almighty Allah has made me a slave of Abu Tharr to such an extent that if he orders me to tear all of you into pieces, I would do so instantly. I swear by that Being, swearing by Whom is the highest of all swearing, and announce that if Abu Tharr requests Almighty Allah giving mediation of Muhammad (s.a.w.s.) and his purified progeny that He may turn the water of all the oceans into the oil of Zambaq and Baan and turn all the mountains into musk, amber and camphor and to turn the branches of all the trees in the world into emeralds, Almighty Allah would never turn down his request and would do whatever he asks.
When Abu Tharr (r.a.) came to the Holy Prophet (s.a.w.s.), the latter told him: O Abu Tharr! Since you have obeyed Allah properly, He has made an animal your slave so that it may prevent your enemies from attacking you and thus you are the best of those persons in whose praise Almighty Allah had said: “…and keep up prayer…”
Source: Tafseer of Imam Hasan Askari(as), Sura Baqara, Verse 3