because
Joshua 14:8
Nevertheless my brethren that went up with me made the heart of the people melt: but I wholly followed the LORD my God.
Joshua 14:9
And Moses sware on that day, saying, Surely the land whereon thy feet have trodden shall be thine inheritance, and thy children's for ever, because thou hast wholly followed the LORD my God.
1 Corinthians 15:58
Therefore, my beloved brethren, be ye stedfast, unmoveable, always abounding in the work of the Lord, forasmuch as ye know that your labour is not in vain in the Lord.