Hadiths: 1.48 and 1.49

1.48:
Narrated `Abdullah bin `Abbas: I was informed by Abu Sufyan
that Heraclius said to him, "I asked you whether they
(followers of Muhammad) were increasing or decreasing. You
replied that they were increasing. And in fact, this is the
way of true Faith till it is complete in all respects. I
further asked you whether there was anybody, who, after
embracing his (the Prophets) religion (Islam) became
displeased and discarded it. You replied in the negative, and
in fact, this is (a sign of) true faith. When its delight
enters the heart and mixes with them completely, nobody can be
displeased with it."

1.49:
Narrated An−Nu`man bin Bashir: I heard Allah's Apostle saying,
'Both legal and illegal things are evident but in between them
there are doubtful (suspicious) things and most of the people
have no knowledge about them. So whoever saves himself from
these suspicious things saves his religion and his honor. And
whoever indulges in these suspicious things is like a shepherd
who grazes (his animals) near the Hima (private pasture) of
someone else and at any moment he is liable to get in it. (O
people!) Beware! Every king has a Hima and the Hima of Allah
on the earth is His illegal (forbidden) things. Beware! There
is a piece of flesh in the body if it becomes good (reformed)
the whole body becomes good but if it gets spoilt the whole
body gets spoilt and that is the heart.