in which he teaches of love between individuals – a natural, unconditional love lasts
Love of one person for another should be a natural love, "Love thy neighbor as thyself", and not a conditional love. That is, to love a person for being a human being, or for his or her qualities, such as wisdom or emotional qualities. But one should not show love because one needs assistance, or to obtain benefit, to soften somebody up to obtain what one wants. Such love is termed conditional love, and is unstable.
Lev Rachav - Tractate Avot, Chapter 5, Verse 17, p. 148. Published by the author, Jerusalem 1992