The meaning of hamd is praise and extolling arising from ones own volition, and from love and veneration of the praised. It also carries the meaning of rida, or contentment, and is the opposite of dhamm, or blame. Its meaning is more general and inclusive than that of shukr, or giving thanks, because it encompasses this as well as having the meaning of praise. (al-Baydawi, vol 1, p45) Furthermore shukr is only expressed as a response to a favour whereas hamd is expressed both as a response to a favour as well as a spontaneous action of dhikr. It is in this respect that ibn Abbas, may Allah be pleased with him, said, ‘al-Hamdullilah is the statement of gratitude.’ Ali, may Allah be pleased with him, said, ‘It is a statement that Allah chose to be directed to Himself and something that He loves.’ Abu Abdur-Rahman al-Jabai said, ‘Prayer is gratitude, any good that we do is gratitude, the most superior form of gratitude is to say, “All praise and thanks are due to Allah” (ibn Kathir vol 1, p44)
Hence it is due to the comprehensiveness of this word that we find the Prophets showing gratitude in the Qur’an by expressing hamd. Allah commanded Nuh, peace be upon him, saying, “… Say: All praises and thanks are due to Allah Who saved us from an oppressive people.” (al-Muminin 23:28) Ibrahim said, “All praise and thanks are due to Allah Who gave me Ismail and Ishaq in my old age…” (Ibrahim 14:39) Dawud, peace be upon him, and Sulayman, pace be upon him, said, “All praise and thanks are due to Allah Who has preferred us above many of His believing servants.” (an-Naml 27:15) Allah commanded our Prophet, peace and blessings of Allah be upon him, saying, “Say:All praise and thanks are due to Allah who has not begotten a son…” (al-Isra 17:11) The People fo Paradise will say, “All praise and thanks are due to Allah Who has removed from us all grief.” (Fatir 35:34) “And the close of their supplication will be: All praise and thanks are due to Allah, the Lord of the Universe.” (Yunus 10:10) It is for this reason that the word hamd has been employed in this verse of al-Fatihah.
Some of the scholars said that shukr is more encompassing than hamd because praise is expressed by the tongue whereas shukr can be expressed by the tongue, heart and limbs. Shukr with the tongue is done by praising the Bestower of blessings; shukr by the limbs is done by acting in obedience to Him and abandoning actions of disobedience; shukr in the heart is done by recognising the magnitude of the blessing and knowing that is has been given by the grace of Allah and not by the servants own merit.
Both opinions are correct in their own place: hamd is more general with respect to when it is done and shukr is more general with respect to how it is done. (al-Baydawi, vol 1, p44)
The Spiritual Cure: An Explanation of Surah Al-Fatihah prepared and translated by Abu Rumaysah Pages 71-74