What did Sam Houston told Jim Bowie to abandon San Antonio ... ?

Because San Antonio was too far from the Texan settlements in the east.

In December 1835, during Texas’ war for independence from Mexico, a group of Texan volunteer soldiers occupied the Alamo, a former Franciscan mission located near the present-day city of San Antonio. On February 23, 1836, a Mexican force numbering in the thousands and led by General Antonio Lopez de Santa Anna began a siege of the fort. Though vastly outnumbered, the Alamo’s 200 defenders-commanded by James Bowie and William Travis and including the famed frontiersman Davy Crockett-held out courageously for 13 days before the Mexican invaders finally overpowered them. For Texans, the Battle of the Alamo became an enduring symbol of their heroic resistance to oppression and their struggle for independence, which they won later that year.