"Hear and understand. It is not what enters one's mouth that defiles that person; but what comes out of the mouth is what defiles one." (Matt 15:10-11)

It was a daily tradition for the Jews to wash their hands before meals; Jesus was aware of the importance of the personal hygiene to the people and there was no exception to His disciples. Since it was a common rule it would happened invariably,

The bible has no record of explaining why hadn’t Jesus’ disciples wash their hands before they ate this time, neither would we know the reason. 

But Jesus was by no means making excuses for His disciples, He was only grabbing the opportunity to express the importance of forethought before one speaks.

The Pharisees took offense after they heard what Jesus said. Jesus’ remarks were exactly pinpointing towards their common problems: Only prone to criticize others, but play dumb to self awareness.  

Jesus said one parable as follow:
"Two people went up to the temple area to pray; one was a Pharisee and the other was a tax collector.

The Pharisee took up his position and spoke this prayer to himself, 'O God, I thank you that I am not like the rest of humanity--greedy, dishonest, adulterous--or even like this tax collector.

I fast twice a week, and I pay tithes on my whole income.'

But the tax collector stood off at a distance and would not even raise his eyes to heaven but beat his breast and prayed, 'O God, be merciful to me a sinner.'

I tell you, the latter went home justified, not the former; for everyone who exalts himself will be humbled, and the one who humbles himself will be exalted." (Lk 18:9-14)
St. Francis who had received the stigmata had declared himself as “little brother”, this is the best way to help humble one’s pride.