Jesus affirmed that we are already made clean by virtue of the Word He proclaimed to us. Therefore, it is not so much rituals that purify the soul, but His Word insofar as we are able to put it into practice. It leads us to have our hearts always set on God alone.
The Word of Jesus is not like human words. Christ is present in his Word, as he is present, although in another way, in the Eucharist. Through his Word Christ enters within us and, provided we allow him to act, he makes us free from sin and therefore, pure of heart.
Thus, purity is the fruit of living the Word, all the Words of Jesus which free us from the so-called attachments, into which we inevitably fall if our heart is not in God and in his teachings. These could be attachments to things, people, ourselves. But if our heart is set on God alone, all the rest falls away.
To achieve this, it can be useful to repeat throughout the day, to Jesus, to God, the invocation of a Psalm which says: “You, Lord, are my only good” (cf. Psalm 16:2)  Let us try to repeat it often, especially when the various attachments seek to pull our heart towards those images, feelings and passions which can blur the vision of good and take away our freedom.
Are we inclined to look at certain advertising posters, to watch certain television programs? No, let’s repeat to him: “You, Lord, are my only good”. Re-declaring our love for God will be the first step towards going out of ourselves. And by doing so we will have gained in purity.
Do we sometimes feel that a person or an activity is coming between us and God, like an obstacle that mars our relationship with him? It is the moment to repeat: “You, Lord, are my only good.” This will help us to purify our intentions and regain inner freedom.
Living the Word makes us free and pure because it is love. The divine fire of love purifies our intentions and all our inner self, because the Bible considers the “heart” to be the deepest seat of intelligence and will.
But there is one love which Jesus commands us to practice and which enables us to live this beatitude. It is mutual love, being ready to give our life for others, following the example of Jesus. It creates a current, an exchange, an atmosphere whose dominant note is precisely that of transparency, purity, because of the presence of God, who alone can make us pure of heart. It is by living mutual love that the Word produces its effects of purification and sanctification.
As isolated individuals we are incapable of resisting at length the solicitations of the world. Instead, mutual love provides a healthy environment capable of protecting the whole of our authentic Christian existence, and in particular, our purity.
(Chiara Lubich, in Parole di Vita, [Words of Life] Città Nuova, 2017, pp. 616-618)