Pope Francis on Friday encouraged 36 new recruits of the Pontifical Swiss Guard to “grow as Christians” during their service in Rome.

The pope, who currently uses a wheelchair due to a knee condition, met with the new candidates for the world’s smallest but oldest standing army on May 6, the day of their swearing-in ceremony.

He said: “Dear Swiss Guards, I encourage you to always place the proper emphasis on formation. The efforts devoted to it are indispensable for acquiring adequate skills and professional competence.”

“But first of all, the time spent in Rome should be valued in order to grow as Christians. I am thinking of the spiritual life, which allows us to discover God’s plan for each of us.”

The Swiss Guards — known for their colorful striped Renaissance-era uniforms — are responsible for Vatican security together with the Vatican gendarmes.

Candidates must meet strict requirements. Each recruit must be a Catholic unmarried male at least 5 feet, 8 inches tall, and between the ages of 19 and 30. Swiss citizenship is required, as is a letter of good standing from the candidate’s pastor.

The pope spoke to the recruits and their families on the anniversary of the Sack of Rome, a battle in 1527 in which 147 Swiss Guards died defending Pope Clement VII from mutinous troops of the Holy Roman Empire.

He said: “Since the institution of the Swiss Guards, many young men have fulfilled the singular function assigned to it, which continues to this day.”

“Through a generous and faithful commitment, over the centuries some have not shirked the hardest trials, going so far as to shed their blood to defend the pope and enable him to carry out his mission in full independence.”

“With this supreme dedication, they have fulfilled what is provided for by the Regulations still in force: the security of the person of the pope and his residence.”

On May 4, the Vatican and the foundation overseeing the renovation of the Swiss Guards’ barracks signed a memorandum of understanding.

The Vatican said that the non-legally binding document expressed both parties’ will to ensure that the Guards have “better and environmentally friendly housing conditions.”

The roughly $60 million building project includes plans to expand the living quarters for guardsmen, some of whom currently sleep in shared rooms or housing outside the Vatican. The new barracks will allow each guard to have a private room with a private bathroom.

The plans have prompted speculation that the new design could accommodate women guards, which would require a change to the corps’ admission requirements.

The memorandum of understanding was related to the fundraising and planning phases of the renovation, reported Vatican News, the Holy See’s online news portal. A second agreement concerning the construction phase will be signed at a later date.

Cardinal Mauro Gambetti, the Archpriest of St. Peter’s Basilica, offered Mass with the Swiss Guards in St. Peter’s Basilica in the morning ahead of the swearing-in ceremony.

Meanwhile, Pope Francis received the Swiss President Ignazio Cassis in a private audience.

The new guards were due to be sworn in at 5 p.m. local time on May 6 in the San Damaso Courtyard of the Apostolic Palace in Vatican City.

The corps said that the ceremony would take place “in reduced form” in the presence of the recruits’ families.

During the ceremony, each recruit approaches the flag of the Swiss Guard as his name is called out. Firmly grasping the banner with his left hand, the new guard raises his right hand and opens three fingers as a sign of his faith in the Holy Trinity.

While holding up his fingers, the guard says: “I, (name), swear diligently and faithfully to abide by all that has just been read out to me, so grant me God and so help me his saints.”

In his address, Pope Francis asked Swiss Guards to pray for one of their colleagues who died recently, according to Vatican News.

He said: “I would like to pause for a moment in pain and sadness. And I would wish that your colleague Silvan Wolf were here present. Unfortunately, he has died, a good, joyful young man. An accident took him away from us. In silence, let us recall Silvan and pray for him.”