The Holy Spirit pours the love of God into our hearts through His grace. That is related to our justification before God. However, this act of the Spirit is not to be conflated with that instance. The manifestation of love in our lives demonstrates that we have been declared righteous by God. The Jamieson-Fausset-Brown Bible Commentary has this excerpt on Matthew 5:43-45:
"45. That ye may be the children--sons. of your Father which is in heaven--The meaning is, "that ye may show yourselves to be such by resembling Him" (compare Mt 5:9; Eph 5:1). for he maketh his sun--"your Father's sun." Well might BENGEL exclaim, "Magnificent appellation!" to rise on the evil and on the good, and sendeth rain on the just and on the unjust--rather, (without the article) "on evil and good, and on just and unjust." When we find God's own procedure held up for imitation in the law, and much more in the prophets (Le 19:2; 20:26; and compare 1 Pe 1:15, 16), we may see that the principle of this surprising verse was nothing new: but the form of it certainly is that of One who spake as never man spake."
"When Jesus spoke to the rich young man, he was equally clear that it is not enough to believe in him (Christ) to have eternal life. That is part of it (John 3:16). But Jesus says it is also necessary to “keep the commandments” and “sell what you possess . . . and follow” him."
A young man who was wealthy approached Jesus Christ and asked Him about what kind of works that he needed to accomplish in order to obtain eternal life (Matthew 19:16). He clearly wanted to earn a right standing before God. In response, Christ revealed that the individual fell short of meeting God's perfect standard of obedience to the Law (Matthew 19:21-22). That is true of us all (Romans 3:23). The disciples marveled at this encounter (Matthew 19:25). He concluded the conversation by reinforcing the fact of the impossibility of salvation apart from the work of God (Matthew 19:26). So, rather than refuting justification by faith alone, this passage actually supports the doctrine.