Matt.10
[34] Think not that I am come to send peace on earth: I came not to send peace, but a sword.
[35] For I am come to set a man at variance against his father, and the daughter against her mother, and the daughter in law against her mother in law.
[36] And a man's foes shall be they of his own household.
O ye of little faith:
Matt.21
[21] Jesus answered and said unto them, Verily I say unto you, If ye have faith, and doubt not, ye shall not only do this which is done to the fig tree, but also if ye shall say unto this mountain, Be thou removed, and be thou cast into the sea; it shall be done.
If you're truly interested in understanding that portion of Matthew, the following excerpt from Bible Gateway's commentary (with related references in parentheses) sums it up well:
Jesus Matters More Than Anything (10:34-39)The demands of the kingdom are so offensive to a world already convinced of its rightness that they provoke that world's hostility.
Opposition from Unconverted Family Members (10:34-37)
Although Jesus values families (5:27-32; 15:4-6; 19:4-9), the division his mission brings is particularly evident in families (compare 10:21; 1 Cor 7:16; of course more people prefer to quote Acts 16:31). Jesus' example demonstrates how this division is accomplished: although we are "harmless" (Mt 10:16; 12:19-20), God's agents proclaim the kingdom uncompromisingly and thus face hostility from others (13:57). Jesus' mission separates us from the values of our society, and society responds with persecution. Jesus selects these specific examples of in-laws (mother-in-law and daughter-in-law) because young couples generally lived with the man's family.
Jesus matters more than the approval or even the civility of our family (10:37). Many viewed honoring one's parents as the highest social obligation (Ep. Arist. 228; Jos. Apion 2.206; Ps-Phocyl. 8); for many, God alone was worthy of greater honor (Deut 13:6; 33:9; 2 Macc 7:22-23).