"The Son of Man came eating and drinking, and they say, 'Look, a glutton and a winebibber, a friend of tax collectors and sinners!' But wisdom is justified by her children."
In this text, Jesus demonstrates the unwillingness of his generation to believe the gospel which he preached. Even with the good fruit which His wisdom produced, the people of his day refused to repent although they stood in the presence of the God-Man. Such hardness of heart is common to all men in all ages of time. Jesus says in Luke 17:26 that
"as it was in the days of Noah, so it will be also in the days of the Son of Man"
And what were the days of Noah like? Genesis 6:5 give us the answer. It is written:
"Then the LORD saw that the wickedness of man was great in the earth, and that every intent of the thoughts of his heart was only evil continually."
In Psalm 51:5, David writes,
"Behold, I was brought forth in iniquity, And in sin my mother conceived me."
Therefore, based on scripture, man is born completely devoid of any goodness within him and, according to Romans 3:11, has no inclination in his heart to seek the Lord. Any attempt by man to work his way to God through self-imposed religion is exposed by scripture as a fraud, for it is written in Isaiah 64:6 that
"all our righteousnesses are like filthy rags"
In light of such truths, salvation by grace appears all the more wonderful. For it was not I who sought God, it was Christ who sought me. It was not I who earned salvation, but Christ who earned it for me. If my salvation was not gained by something good I did, neither shall it be lost by something bad I have done. It is written in Romans 5:8,
"But God demonstrates His own love toward us, in that while we were still sinners, Christ died for us."