Ques. In what way can the Christian throw his pearls before swine, or give the holy things to dogs?
Ans. Matthew 7:6. By arguing and discussing the precious things of God with unconverted men, or pressing truth, precious in itself, on those who are not exercised about it. We need to bear a testimony in this world to those around, but it is to be in the spirit of meekness, and with prayer that we may minister the right word. 2 Timothy 2:23-26.
Ques. Was it disobedience on the part of the healed ones in the gospels in not heeding the Lord's charge to say nothing about their being healed? Why is it mentioned in one gospel and not in another?
Ans. The Lord had always a reason for telling anyone not to speak about what had been done. Sometimes it was because He was rejected. Other times, because as a Servant, He was hiding Himself. This is especially true in Mark's gospel. You should specify what instances you desire light about.
Those who were healed and told it did disobey, but acted out of the fullness of their gratitude, and failed to enter into His purpose at the moment.