The Old Testament is the Word of God and is still applicable to us as God’s people. We consider how much of the Old Testament applies, which parts of it do and which do not.
We see two things:
Why were the disciples of John so concerned over their religious fasting? Why were Matthew and the disciples all feasting? Because they understood that only by loving and following the Lord they would have eternal life. Therefore, if you aren’t trusting Jesus, do so now.