And he said to his disciples, "Temptations to sin (Greek: stumbling blocks) are sure to come; but woe to him by whom they come! It would be better for him if a millstone were hung around his neck and he were cast into the sea, then that he should cause one of these little ones to sin. Take heed to yourselves; if your brother sins, rebuke him, AND IF HE REPENTS, forgive him; and if he sins against you seven times in the day, and turns to you seven times, and says 'I repent,' you MUST forgive him."
Luke 17: 1 - 4
On this Jesus is talking about temptations, but plainly on those who cause sin, rather then those who fall into it, for we all sin. Mostly though he is pointing out forgiveness, for if you know you have done wrong, and do not ask for forgiveness (repent to the lord and/or the person you have sinned against), then you cannot be saved. Remember Jesus says to us if that person repents, "You MUST forgive him." At the end of verse four.
The apostles said to the Lord, "Increase our faith!" And the Lord said,"If you had faith as a grain of mustard seed, you could say to this sycamine tree, 'Be rooted up, and be planted in the sea,' and it would obey you.
Luke 17: 5 and 6
Clearly he is saying to us all, that without God (in whom we place our faith) we could do nothing of any use. It's interesting to think that if we had that much faith, and the lords will behind what we wanted to do, what can be done.