Today we celebrate The Ascension Of The Lord, commemorating the Ascension of Christ into heaven, according to Mark 16:19, Luke 24:51, and Acts 1:2.
Why is Jesus’s Ascension important? Well, here’s Bishop Barron’s thoughts. Also, here’s what the CCC says...
665 - Christ's Ascension marks the definitive entrance of Jesus' humanity into God's heavenly domain, whence he will come again (cf. Acts 1:11); this humanity in the meantime hides him from the eyes of men (cf. Col 3:3).
666 - Jesus Christ, the head of the Church, precedes us into the Father's glorious kingdom so that we, the members of his Body, may live in the hope of one day being with him for ever.
667 - Jesus Christ, having entered the sanctuary of heaven once and for all, intercedes constantly for us as the mediator who assures us of the permanent outpouring of the Holy Spirit.
- The Catechism of the Catholic Church
The observance of this feast is very old. It predates St. Augustine in the 5th century. Augustine in his writing refer to it as being of Apostolic origin, and said it was a universal observance of the Church long before his time
“He ascended into Heaven and is seated at the right hand of the Father.”
-The Apostles Creed