(This may turn into Walter Chantry week due to the many great passages I highlighted recently while reading his book Today's Gospel)
"When Abraham attempted to hasten the arrival of an heir, he produced Ishmael, 'a wild man' [Genesis 16:12]. He used a fleshly procedure and secured a fleshly offspring. As God so plainly reminds us, 'They which are the children of the flesh, these are not the children of God.' [Romans 9:8]. However much Abraham might declare to Ishmael that he was a beloved son, God would disown him. Modern evangelism is filling the church with Ishmael's. Because of fleshly haste, evangelists produce 'converts' whom they call sons. But God will not own them. He is looking for Isaacs. When children are born through God-appointed techniques, then God will Himself assure them that they are heirs to the promises."
-Walter Chantry, Today's Gospel Authentic or Synthetic