How do you know whether you have received the Holy Spirit? Question your heart. If you love your brother and sister, the Spirit of God abides in you. Examine yourself before the eyes of God; see if there is in you a love of unity of peace, and a love for the church spread throughout the whole world.
Take care not to love only the person in front of you: we do not see many sisters and brothers, but we are united to them in the unity of Spirit. What cause is there to marvel that they are not with us? We are in one body; we have one head in heaven.
So, if you want to know if you have received the Holy Spirit, ask your heart: if fraternal charity is there, you can rest easy, for there can be no love without the Holy Spirit. As St. Paul says, the charity of God is poured forth in our hearts by the Holy Spirit who is given to us. (Romans 5:5)
Easter Meditations From the Vita Christi
Ludolph of Saxony
Quoted in “Your Hearts Will Rejoice”