There is an ancient Roman tradition of visiting the altars of seven churches on Holy Thursday night. This is actually pretty easy to do in a city of 900 churches. After the Mass of the Lord's Supper on Holy Thursday evening, the last Mass before the Easter Vigil on Saturday night, the Blessed Sacrament is reserved in a side chapel or altar. The Mass of the Lord's Supper commemorates especially the institution of the Eucharist, and the Church encourages devotion to the Blessed Sacrament on this day. There is also a practical aspect--the Church often mixes the symbolic or devotional with the practical. The altar needs to be stripped and the tabernacle emptied for the Good Friday liturgy. Over the years, the people and parishes added splendor to this, decorating the altar with candles, flowers, and beautiful cloths. And so developed the custom, especially in Rome and then spreading to other cities, of visiting Christ in the Sacrament at a variety of different altars and churches.
The custom developed of visiting seven churches. Why seven? This is probably a confusion with another custom, that of visiting the
seven pilgrimage churches of Rome when on pilgrimage there. The visiting of these seven churches was often associated with a plenary indulgence.
There may have been an indulgence associated with the Holy Thursday custom of visiting churches, but there is no more. Rather, the Church offers a
plenary indulgence for the following in Holy Thursday:
A plenary indulgence is granted [under the normal conditions] for the faithful who piously recite the versus of the Tantum ergo after the Mass of the Lord's Supper on Holy Thursday during the solemn reposition of the Most Blessed Sacrament.
Here were the seven churches I visited this Holy Thursday here in Rome:
