This is the biblical source for the Priestly Blessing.

Before carrying out this ordinance the Cohanim recite a blessing similar to that said prior to carrying out any other commandment: “Blessed are you O Lord, who has consecrated us with His commandments and commanded us to bless His people Israel with love”.

However, the concluding words of this blessing “with love” are somewhat perplexing, since nowhere apparently does it say in the Torah that the blessing should be given with love. 

An intriguing answer is given by Rabbi Shlomo Riskin, the Chief Rabbi of Efrat, in  the name of Rabbi Piattelli, Rabbi of Venice, Italy. Rabbi Piattelli suggests an etymological connection between the Hebrew word that is used here in the Torah for “say”,  amor,  and the Italian word amore, love. 

The words amor lahem do not merely mean “say it (the blessing) to them” but rather “say it with love”.

This is consistent with the way our sages treat words derived from the root a-m-r. In several places our sages stress that the word means “saying kindly”. It also explains, for instance, why the word taggid is used in relation to Moses teaching men, but tomar in relation to him teaching women. 

Both words mean “to say” but while taggid suggests speaking harshly, tomar suggests a kinder and gentler approach.  In fact, the Pesikta (a midrashic collection) suggests precisely that about the word amor mentioned in regards to the Priestly Blessing. 

Be this as it may, according to the Torah the proper relationship between the priests and the common people should be one of love. The task given to the priests is to bless the people and to do so with love. 

Likewise, the main task of a spiritual leader is not to rebuke the people but rather to be there for them in a loving, caring manner.