Is there a Hadith stating that the Prophet (peace be upon him) commanded a Companion to divorce his barren wife, even though he loved her, and if so, why?

The Hadith "Marry the barren woman" is not authentically reported in the Sunnah. However, the questioner might be referring to the Hadith of Ma'qil ibn Yasar, reported by Abu Dawud and others: "Marry the affectionate and fertile women, for I shall outnumber the nations with you." This Hadith and others indicate the desirability of marrying a fertile woman. Marrying a barren woman is contrary to what is preferable, but it is not forbidden or disliked. The consulted one is entrusted, so he should advise what is best. If the woman is barren, then he should marry a barren woman like her, or combine her with a fertile woman to achieve procreation.