In the old testament, God stated several times that He was a jealous God. This simply means that God wants what belongs to Him. Take the passage of Exodus 34:4, "For thou shalt worship no other god: for the LORD, whose name is Jealous, is a jealous God:" God does not want us to worship any other entity but Him. As Lord of heaven and earth He is worthy of all worship. Knowing this, we need to put God first. God deserves our loyalty above all else. When we understand this principle, we can understand the last few passages of Luke 9.
In these verses Christ is calling to men. He is asking them to follow Him and preach the kingdom of God. One man declares that He must first bury His father and another says, "Lord, I will follow thee; but let me first go bid them farewell, which are at home at my house." Jesus replies with the statement, "No man, having put his hand to the plough, and looking back, is fit for the kingdom of God." We may react, "How harsh! The man only wanted to say goodbye." But we forget who gave the command to follow. God asked the man to follow Him. We must never hesitate at God’s call. Those who consider others before considering Christ will not be fit for the kingdom.
I would like to encourage you, follow Christ alone. Do not be distracted by the things of this world, or other obligations. Our only obligation is to follow Christ. He is first. If we follow Him alone we will be able to say, as Peter said, "we have left all, and have followed thee." (Mark 10:28) Jesus’ reply is a promise for all who will follow Him.
And Jesus answered and said, Verily I say unto you, There is no man that hath left house, or brethren, or sisters, or father, or mother, or wife, or children, or lands, for my sake, and the gospel’s, but he shall receive an hundredfold now in this time, houses, and brethren, and sisters, and mothers, and children, and lands, with persecutions; and in the world to come eternal life.
– Mark 10:30