Part of a poem written by St. Francis himself 

Most High, all powerful, good Lord,
to you be the praise, the glory and the honour and every blessing.

May you be praised, My Lord, through all your creatures,
especially Sir brother sun, through whom you lighten the day for us.

He is beautiful and radiant with great splendour.
He signifies you, O Most High.
Be praised, my Lord, through sister moon and the stars,
In the heavens they are clear and precious and lovely.

Be praised, my Lord, through brother wind
and by air and clouds, clear skies and all weathers,
through which you sustain your creatures. 

Be praised, my Lord, through sister water,
who is very useful and humble and precious and pure. 

Be praised, my Lord, through brother fire,
by whom the night is illumined for us,
he is beautiful and cheerful, full of power and strength. 

Be praised my Lord through our sister mother earth,
who sustains and governs us
and produces different fruits with coloured flowers and grass. 

Praise and bless my Lord and give him thanks
and serve him with great humility.

From the first biography of St. Francis (Thomas of Celano)
When the brothers are cutting wood he asks them not to cut down the whole tree, so that it has hope of sprouting again. He asks the brother doing the gardening not to dig the edges of the garden, so that in springtime the greenery of the grass and the beauty of the wild flowers may proclaim the beautiful Father of all. He picks up little worms from the road so they will not be trampled underfoot. He calls all creatures brothers and sisters.

Also from the first biography of St. Francis
Francis was travelling through the Spoleto valley and reached a place near to Bevagna, where a large flock of different types of birds had gathered, including doves, crows, and others commonly called magpies. When Francis, the most blessed servant of God, saw them, he ran quickly to them, leaving his companions on the road. He was a very passionate man with strong feelings of kindness and tenderness even towards creatures in the natural creation unable to reason. When he got closer he could see that they were waiting for him, so he greeted them in his usual way (‘The Lord give you peace’). He was quite surprised, however, because the birds did not fly away as they usually do. Filled with great joy, he humbly asked them to listen to the word of God.
Along with many other things he said to them, ‘My brother and sister birds, you should praise your Creator from the bottom of your heart, and love him always. He gave you feathers to wear, wings to fly, and whatever you need. God made you a noble branch of his creatures and gave you a home in the purity of the air, so that, although you do not sow or reap he still protects and cares for you without you needing to worry at all.’ He himself, and those brothers who were with him at the time, used to say that, when Francis said those words the birds showed their joy in their own wonderful way. They stretched their necks, spread their wings, opened their beaks and looked at him. He walked up and down through the flock, touching their heads and bodies with his clothes. Then he blessed them, made the sign of the cross over them, and gave them permission to fly away.

From ‘The little flowers of St. Francis’
A large wolf appeared in Gubbio which was killing people as well as animals. Francis went to meet the wolf, although everyone had advised him not to do so. The wolf ran towards St Francis to attack him but Francis made the sign of the cross and shouted to him, ’Come here brother wolf; I command you in the name of Christ not to harm me nor anybody else.’ The wolf came to a halt and lay down at Francis’ feet. Francis told him, ‘Brother wolf, you have done a lot of harm here, killing God’s creatures without his permission and even people. All the inhabitants of this city are your enemies, but I will make peace between them and yourself, brother wolf.
If you are willing to make this peace, I promise that you will be fed every day by the inhabitants of this city, as it is hunger which has made you do so much harm; but if I obtain all this for you, you must promise, on your side, never again to attack any animal or any human being; do you make this promise?" Then the wolf, bowing his head, made a sign that he consented.
They then went together back to the citizens, to whom St. Francis said, ‘Listen my brothers and sisters: the wolf who is here before you has promised and pledged his faith that he consents to make peace with you all, and no more to offend you in any way, and you must promise to give him each day his necessary food.’ Then all the people promised with one voice to feed the wolf to the end of his days.
The wolf lived two years at Gubbio; he went familiarly from door to door without harming anyone, and all the people received him courteously, feeding him with great pleasure, and no dog barked at him as he went about. At last, after two years, he died of old age, and the people of Gubbio mourned his loss greatly; for when they saw him going about so gently amongst them all, he reminded them of the virtue and sanctity of St Francis.