The last part of the Communion service in the classical prayer books is the Blessing. Specifically, this one (albeit with the 2019 wording)…
The peace of God, which passes all understanding, keep your hearts and minds in the knowledge and love of God, and of his Son Jesus Christ our Lord; and the blessing of God Almighty, the Father, the Son, and the Holy Spirit, be among you, and remain with you always. Amen.
Once this blessing is pronounced, people can get up and go.
Except, in the modern order, we now have an extra Dismissal that follows, and usually music as well. But until the 1970’s (or perhaps the arrival of something like the Anglican Missal?) the Blessing marked the end of the liturgy.
I have heard it argued that the priest offering a Blessing at this point is redundant – what greater blessing could be conferred than receiving the Body and Blood of our Lord? But there are a couple different answers.
First of all, ending a worship service with a blessing is biblical. It is the Old Testament pattern – even though the sacrifice of animals and their oblation in the Temple and the eating of the meat was the “high point” of the Old Covenant liturgy, the priest was still to bless the people after. It is the New Testament pattern too, in a way: St. Paul ended each of his epistles with a blessing of some sort. It is a little ironic, though, that the blessing we use is not explicitly used as a blessing by St. Paul (cf. Philippians 4:7 – it was actually the Epistle reading a couple Sundays ago).
Secondly, the specific content of this blessing is appropriate. In a general sense, the argument against a blessing after receiving Holy Communion does sound logical, but this objection is undermined by what this blessing calls for: that the people would be kept in the knowledge and love of God. It is a blessing of perseverance – may the people, who have just celebrated their unity with and in Christ, always remain so.
Third, and finally, it is analogous to the Prayer of Humble Access. If you reduce the meaning of this blessing to some sort of generic blessing, then yeah it’s lame. Same deal with the Prayer of Humble Access: if you reduce the meaning of that prayer to some sort of generic confession, then it’s redundant and silly too. But both of these prayers, although bearing similarities to other prayers and “functions” within the service, bring new and different lights to the table (or, from the Table in this instance).
Now, all that having been said… the 2019 Prayer Book states that
The Bishop, when present, or the Priest, gives this or an alternative blessing
But what is an “alternative blessing”? None is supplied. In the classical prayer books this choice didn’t exist: that blessing was the blessing. But there is another blessing in the old prayer book tradition – the Burial Office ends with a different blessing, also found at the end of the Committal in the 2019 Prayer Book:
The God of peace, who brought again the from the dead our Lord Jesus Christ, the great Shepherd of the sheep, by the blood of the eternal covenant, make you perfect in every good work to do his will, working in you that which is well-pleasing in his sight…
Notice in both blessings that these are not (strictly-speaking) prayers. “May God ___” is a prayer, but these are more like statements (or perhaps subjunctive verbs, if I remember my grammar correctly): “God… make you perfect” and “the peace of God… keep your hearts and minds.” Blessings are “speech-acts”, like when a minister declares a man and a woman husband and wife, or baptizes somebody. However sacerdotal you may or may not choose to view these “sacramental rites”, the reality is that these are special acts of the Church through her ordained ministers. Pentecostalism, especially in its Prosperity Gospel extreme versions, has yielded an unhealthy practice that is creeping into evangelicalism: “declarations” in the name of Jesus for one or another sort of blessing. This practice is essentially usurping the special role of the ordained clergy, popularizing it for all Christians, and reducing its gravity and import often to crass hopes and dreams for health and wealth. Be very careful what you do, or permit, along these lines in your ministry context.
One last note about the option for different blessings at the end of the Communion service. I strongly suspect that the main reason the 2019 rubric permits an “alternative blessing” is to authorize the Seasonal Blessings that have been provided in supplemental books such as Book of Occasional Services and Common Prayer (2000). If you are so inclined, you can peruse those materials for a variety of blessings – probably finding a unique one for every Sunday of the year. Although modern liturgy trends seem to prefer such variety, classic Prayer Book wisdom does not support this, so I would advise priests not to deviate from the standard Prayer Book blessing very often. Maybe grab a “solemn blessing” for Christmas Day and Easter Day; maybe use another blessing from the Bible or pre-existing tradition on other special and rare occasions; otherwise, be sure to use the standard historic blessing virtually all year.
If it’s always changing, it’ll never stick in the people’s minds, and go in one ear and out the other. And, given the fact that the standard blessing is for our hearts and minds to kept, that would be sadly ironic indeed.