Having a firm mental grasp or acquiring information is expressed by ἐπίσταμαι (epistamai). Its root means to stand (ιστημι). Therefore, it expresses standing with a firm mental grasp because of the information a person is acquainted with.
In Peter’s denial of Christ, when questioned by a young servant girl if he was with Christ, he adamantly denied it, saying that he neither intuitively knows nor has acquired knowledge concerning Christ, Mark 14:68. After Peter is restored from the attack by Satan that caused him to deny Christ, God uses him to show the Jews that the Gentiles are also being accepted into the Church. In Cornelius’ house, Peter states that they have a firm mental grasp on the fact that it is not permissible for a Jew to fellowship or enter into a place with another nation, Acts 10:28. However before Cornelius sent for Paul, God showed him that he is not to call any man common or unclean and, therefore, Peter came without objection.
During the council in Acts chapter fifteen concerning whether or not the Gentiles should be circumcised and obey the law of Moses, Peter spoke up concerning what God had been doing. The elders and apostles present had acquired knowledge concerning the situation when God instructed Peter to enter into the house of a Gentile so they could hear the gospel. They were neither circumcised nor immersed before the Holy Spirit came upon them in the same manner as He did on the day of Pentecost to show the Jews a sign, Acts 15:5.
When Apollos came to Ephesus, he was mighty in the Scripture; however, he was only familiar with (had a firm mental grasp) the immersion of John, Acts 18:25. Aquila and Priscilla took him aside and explained the way of God to him so that he acquired more accurate information concerning all that God had done since the immersion of John.
The seven sons of Sceva, who were known as exorcists, sought to use the name of Jesus against a malignantly evil spirit who was possessing man and found out that it is not the name alone but the relationship that matters. After they told the spirit that he was to leave by the authority of the Jesus that Paul preaches, the demon responded, “ I experientially know Jesus, and Paul I have acquired knowledge concerning, but who are they?” He then overpowered them and sent them running down the street without their clothing, Acts 19:15.
Those who teach contrary to proper godliness are puffed up and not acquainted with the truth, 1 Timothy 6:3. They are obsessed with disputing and arguing over words, producing envy, strife, revelings, and malignantly evil suspicions. They suppose gain is godliness. We are to withdraw from such false teachers. They speak of things they are not acquainted with and corrupt themselves in their error, Jude 10. Let us not be fooled by those who seek to make merchandise of us. Since we have not gained a firm mental grasp on what will happen tomorrow, and our lives are but a vapor that appears for only a short time, James 4:14, let us seek out the desirous will of God and live a life of godliness with contentment, 1 Timothy 6:6, for we brought nothing into this world, and will take nothing from it, 1 Timothy 6:7.